The number one rule (or at least close to the number one rule) is to design for your users. If you read the criteria as was suggested here already, it's all about usability. Here are some things to keep in mind...
- Is it easy to navigate?
- Is the content presented in a logical manner?
- Is the content relevant?
- Is it visually interesting?
- Am I retaining users?
- Is my team using it?
- What did I learn about FIRST?
Your website is a resource for your team. Other teams will visit, but your focus is that this is a team resource. Don't forget that your "Team" includes the parents, your mentors and your sponsors. You are designing to make them ALL happy. You want the team parents using the site and you want your sponsors linking to your site. Your site is an easy way to show your appreciation to your sponsors.
It's important to add new content. Keep it up to date and you will keep users coming back to it. Web design is unique in that a site is never "done". If you don't present new content for you users, there is no reason for them to return.
One thing a lot of web designs forget to offer as a backup to your navigation is a site-map. It is an easy way to keep the search engines happy if you are using frames. It will allow that full content to be indexed.
Offer some way to search your site. Google offers a free script to do this. Look here for more info
http://www.google.com/searchcode.html
hth