Facebook gives you three ways to search for groups you'd like to join:
Browse based on a handful of criteria. Unless you know the name or subject of the group you're looking for (in which case, try the next option), this is the quickest way to find a group.
Search for specific groups and topics. If your buddy told you the name of a group you want to join or if you're interested only in groups devoted to a specific subject—like the music of Todd Rundgren—this is your quickest option.
View the most popular groups on the site. Finding out which groups your fellow network members have joined during"the last 24 hours is interesting, even if you decide not to follow their lead.
Another way to join a Facebook group is to respond to an invitation sent by another member (see Inviting People to Join A Group).
Browsing lets you see a listing of all the groups associated with a particular network—for example, only groups created by people who live in your area—and a particular category, such as food & drink, self-help, and so on. To browse for groups:
In the Applications menu on the left side of the Facebook main menu, click Groups. The left side of the Groups page that appears shows you what groups your friends have joined, which can be interesting; the right side shows the groups you've already joined.
On the Groups page, click ...