When you open up a forum, you'll see a list of threads with an envelope to the left of the subject of the thread. A red envelope is a "hot" topic. I think it turns into a hot topic with around 100 people viewing it. A gray envelope is not a hot topic yet. Knowing this, if you're busy, you can look and see what the "hot" topics are that others are looking at more often.
You can go to the very top of the forums's page, where there's a white "Forum" box on the far left of the page. Under that, is "New Posts". Going there, you will see posts made since the last time you visited the site. Also along that row, with New Posts, is the "Calendar". Many events going on around FAA, including Online Support's areas, can be found posted there. There's also an area for "Community", where you can find an alphabetical listing of members. Only registered members can view the Community area.
When you're on the main forum page, the emblem/box next to the forum's title will be either blue or gray. Blue boxes are forums that have new posts since the last time you visited. Gray boxes don't have any new posts, so you don't have to bother opening up those forums.
On the far top right of the page you can click on "Settings". If you don't receive e-mail notifications of replies to threads you've posted in, you may very well have a listing of them here. Or at least, I do, and I don't remember doing anything special to have this happen.
Stickies are important threads (announcements) that the Administration wants to be immediately viewable when opening up a forum. You will find the same stickies at the top of all pages of the forum. If the sticky has a lock on the top right of it, no replies are permitted (although you can always post a question in the "regular" part of the forum). If there's no lock, replies are permitted and will be responded to by an FAA Online Support Outreach Member. The colors of the sticky envelopes are the same: red for hot topics, gray for not hot ones.
A little green arrow on the bottom right of a thread topic means a topic you yourself have posted in. This can be helpful in quickly identifying threads you are interested in.
While on the Main Forum page, you can scroll down to the bottom and see some interesting statistics. Who's online at the moment is there, along with the number of guests currently on the site. You can also see how many threads, posts, and members FAA Online Support has. If there's a Calendar event that day, it will be listed there as well.
Hovering over a symbol will often bring up what that symbol stands for.
Hope this helps. If you have any questions, please feel free to post them here!