Today, I watched an enlightening session on Usability Testing by Steve Krug. Usability is an attribute of good design. A thing is usable if a person of average ability and experience can figure out how to use it for its intended purpose without it being more trouble than it's worth.
UX issues:
Sometimes they are annoying
Sometimes they cause anxiety
Sometimes they scare us off
A usability test is wtching people try to use what you create while thinking out loud
Six Maxims from Rocket Surgery Made Easy
Start earlier than you think makes sense
A morning a month, that's all we ask
Recruit loosely and grade on a curve
Make it a spectator sport
Focus ruthlessly on a small number of the problems
When fixing problems, always do the least you can.
Tweak, don't redesign
Recommended Books
Letting Go of the Words by Janice Redish
UX for lean startups by Laura Klein
References
Usability Testing: How to Do-It-Yourself with Steve Krug