Be sure to include your organization's mission and a vision.
Hire competent people
Hire passionate, caring people
Hire meticulous, attentive people
Consider users ages
Consider users knowledge level
Consider users patience level
Establish your site's purpose
Decide on how you will achieve this purpose (Push-Pull of data/information/knowledge)
Create a simple, navigable structure
Mind the taxonomy: Use metatags appropriately to ease searching
Use common words or words associated with specialized terms (if you must have "sphygnonometer," be sure to tag it with "stethescope.")
Refer to the likes of Library of Congress for cataloging knowledge and DDMS for naming conventions.
Not everyone has a PhD. Keep it simple.
Quickest route to the data/information/knowledge is the fastest way to people's hearts.
Use appropriate hardware to avoid downtime.
Use good applications to achieve the above goals.
Keep the animated graphics down. Getting motion sick while researching is not fun.
Remember that people may access on their smart phones-small screens. Be brief.