This Presentation base on Joshua Porter Blog (http://bokardo.com/principles-of-user-interface-design/)

1. “ To design is much more than simply
to assemble, to order, or even to edit;
it is to add value and meaning, to
illuminate, to simplify, to clarify, to “
modify, to dignify, to dramatize, to
persuade, and perhaps even to amuse.
- Paul Rand
Principles
UI Design
Joshua Porter
Director of UX at HubSpot, Co-founder @performable, Founder @bokardo & Co-founder @52weeksofux

2. Clarity is job
Clarity is the first and most important job of any interface. To be effective using
an interface you've designed, people must be able to recognize what it is, care
about why they would use it, understand what the interface is helping them
interact with, predict what will happen when they use it, and then successfully
interact with it. While there is room for mystery and delayed gratification in
interfaces, there is no room for confusion. Clarity inspires confidence and leads
to further use. One hundred clear screens is preferable to a single cluttered one.

3. Interfaces exist to
enable interaction
Interfaces exist to enable interaction between humans and our world. They can
help clarify, illuminate, enable, show relationships, bring us together, pull us
apart, manage our expectations, and give us access to services. The act of
designing interfaces is not Art. Interfaces are not monuments unto themselves.
Interfaces do a job and their effectiveness can be measured. They are not just
utilitarian, however. The best interfaces can inspire, evoke, mystify, and intensify
our relationship with the world.

4. Conserve attention
at all costs
We live in a world of interruption. It's hard to read in peace anymore without
something trying to distract us and direct our attention elsewhere. Attention is
precious. Don't litter the side of your applications with distractible
material…remember why the screen exists in the first place. If someone is
reading let them finish reading before showing that advertisement (if you must).
Honor attention and not only will your readers be happier, your results will be
better. When use is the primary goal, attention becomes the prerequisite.
Conserve it at all costs.

5. Keep users in control
Humans are most comfortable when they feel in control of themselves and their
environment. Thoughtless software takes away that comfort by forcing people
into unplanned interactions, confusing pathways, and surprising outcomes. Keep
users in control by regularly surfacing system status, by describing causation (if
you do this that will happen) and by giving insight into what to expect at every
turn. Don't worry about stating the obvious…the obvious almost never is.

6. Direct manipulation
is best
The best interface is none at all, when we are able to directly manipulate the physical objects in our
world. Since this is not always possible, and objects are increasingly informational, we create
interfaces to help us interact with them. It is easy to add more layers than necessary to an interface,
creating overly-wrought buttons, chrome, graphics, options, preferences, windows, attachments, and
other cruft so that we end up manipulating UI elements instead of what's important. Instead, strive
for that original goal of direct manipulation…design an interface with as little a footprint as possible,
recognizing as much as possible natural human gestures. Ideally, the interface is so slight that the
user has a feeling of direct manipulation with the object of their focus.

7. One primary action
per screen
Every screen we design should support a single action of real value to the
person using it. This makes it easier to learn, easier to use, and easier to add to
or build on when necessary. Screens that support two or more primary actions
become confusing quickly. Like a written article should have a single, strong
thesis, every screen we design should support a single, strong action that is its
raison d'etre.

8. Keep secondary
actions secondary
Screens with a single primary action can have multiple secondary actions but
they need to be kept secondary! The reason why your article exists isn't so that
people can share it on Twitter…it exists for people to read and understand it.
Keep secondary actions secondary by making them lighter weight visually or
shown after the primary action has been achieved.

9. Provide a natural
next step
Very few interactions are meant to be the last, so thoughtfully design a next step
for each interaction a person has with your interface. Anticipate what the next
interaction should be and design to support it. Just as we like in human
conversation, provide an opening for further interaction. Don't leave a person
hanging because they've done what you want them to do…give them a natural
next step that helps them further achieve their goals.

10. Appearance follows
behaviour
Humans are most comfortable with things that behave the way we expect. Other
people, animals, objects, software. When someone or something behaves
consistently with our expectations we feel like we have a good relationship with
it. To that end designed elements should look like how they behave. In practice
this means that someone should be able to predict how an interface element will
behave merely by looking at it. If it looks like a button it should act like a button.
Don't get cute with the basics of interaction…keep your creativity for higher order
concerns.

11. Consistency matters
Following on the previous principle, screen elements should not appear
consistent with each other unless they behave consistently with each other.
Elements that behave the same should look the same. But it is just as important
for unlike elements to appear unlike (be inconsistent) as it is for like elements to
appear consistent. In an effort to be consistent novice designers often obscure
important differences by using the same visual treatment (often to re-use code)
when different visual treatment is appropriate.

12. Strong visual
hierarchies work best
A strong visual hierarchy is achieved when there is a clear viewing order to the visual elements on a
screen. That is, when users view the same items in the same order every time. Weak visual
hierarchies give little clue about where to rest one's gaze and end up feeling cluttered and confusing.
In environments of great change it is hard to maintain a strong visual hierarchy because visual
weight is relative: when everything is bold, nothing is bold. Should a single visually heavy element
be added to a screen, the designer may need to reset the visual weight of all elements to once again
achieve a strong hierarchy. Most people don't notice visual hierarchy but it is one of the easiest
ways to strengthen (or weaken) a design.

13. Smart organization
reduces cognitive load
As John Maeda says in his book Simplicity, smart organization of screen elements can
make the many appear as the few. This helps people understand your interface easier
and more quickly, as you've illustrated the inherent relationships of content in your
design. Group together like elements, show natural relationships by placement and
orientation. By smartly organizing your content you make it less of a cognitive load on
the user…who doesn't have to think about how elements are related because you've done
it for them. Don't force the user to figure things out…show them by designing those
relationships into your screens.

14. Highlight, don't
determine, with color
The color of physical things changes as light changes. In the full light of day we
see a very different tree than one outlined against a sunset. As in the physical
world, where color is a many-shaded thing, color should not determine much in
an interface. It can help, be used for highlighting, be used to guide attention, but
should not be the only differentiator of things. For long-reading or extended
screen hours, use light or muted background colors, saving brighter hues for
your accent colors. Of course there is a time for vibrant background colors as
well, just be sure that it is appropriate for your audience.

15. Progressive disclosure
Show only what is necessary on each screen. If people are making a choice,
show enough information to allow them the choice, then dive into details on a
subsequent screen. Avoid the tendency to over-explain or show everything all at
once. When possible, defer decisions to subsequent screens by progressively
disclosing information as necessary. This will keep your interactions more clear.

16. Help people inline
In ideal interfaces, help is not necessary because the interface is learnable and
usable. The step below this, reality, is one in which help is inline and contextual,
available only when and where it is needed, hidden from view at all other times.
Asking people to go to help and find an answer to their question puts the onus
on them to know what they need. Instead build in help where it is needed…just
make sure that it is out of the way of people who already know how to use your
interface.

17. A crucial moment:
the zero state
The first time experience with an interface is crucial, yet often overlooked by
designers. In order to best help our users get up to speed with our designs, it is
best to design for the zero state, the state in which nothing has yet occurred.
This state shouldn't be a blank canvas…it should provide direction and guidance
for getting up to speed. Much of the friction of interaction is in that initial
context…once people understand the rules they have a much higher likelihood of
success.

18. Existing problems
are most valuable
People seek out solutions to problems they already have, not potential problems
or problems of the future. Therefore, resist creating interfaces for hypothetical
problems, observe existing behavior and design to solve existing problems. This
isn't as exciting as blue sky wondering but can be much more rewarding as
people will actually use your interface.

19. Great design is
invisible
A curious property of great design is that it usually goes unnoticed by the people
who use it. One reason for this is that if the design is successful the user can
focus on their own goals and not the interface…when they complete their goal
they are satisfied and do not need to reflect on the situation. As a designer this
can be tough…as we receive less adulation when our designs are good. But great
designers are content with a well-used design…and know that happy users are
often silent.

20. Build on other design
disciplines
Visual and graphic design, typography, copywriting, information architecture and
visualization…all of these disciplines are part of interface design. They can be
touched upon or specialized in. Do not get into turf wars or look down on other
disciplines: grab from them the aspects that help you do your work and push on.
Pull in insights from seemingly unrelated disciplines as well…what can we learn
from publishing, writing code, bookbinding, skateboarding, firefighting, karate?

21. Interfaces exist to
be used
As in most design disciplines, interface design is successful when people are
using what you've designed. Like a beautiful chair that is uncomfortable to sit in,
design has failed when people choose not to use it. Therefore, interface design
can be as much about creating an environment for use as it is creating an
artifact worth using. It is not enough for an interface to satisfy the ego of its
designer: it must be used!