My opinion is that ideally recruiting for this upcoming years team began the moment you formed this previous years team. I've condensed the whole process to what I think are the most important points and time lines:
1) Always be thinking of recruitment even if it's not in an active capacity.
-If your team only presents itself to your school during recruitment periods, it can be difficult to express the depth of FIRST, and your team could be lost in the wash of other teams and clubs.
-Keep the media that your team is published in or develops. This is invaluable to show at presentations and pretty much anywhere. Plus if you're like me, you can't get to sleep until you look at the framed picture of your robot that's next to your bed.
2) Adopt a more longitudinal view of recruitment.
-Lego league teams and team demonstrations as well as a "club day" for 8th graders, like that mentioned above can interest prospective students well before they're in High School. Plus if you volunteer at these (our team doesn't require attendance), you get that neat happy feeling when all the kids faces light up when the robot turns on .
3) Recruitment doesn't have to have a set time
-We recruit the majority of our new members at the beginning of the school year, and have a recruitment meeting where we distribute sign up forms early on (9/8/05 this year). We do however have a sign-up period at the end of the year, so students already at the high school (a.k.a. not 8th graders) can sign up and participate in a few extra off-season competitions to get a feel for FIRST. All new members have the opportunity to attend 2-3 off season competitions, as well as Ramp Riot, which we host.
4) If a student shows up at your recruitment meeting, they're interested.
-I haven't seen this with robotics, but I've seen other groups try to sell themselves to me after I voluntarily sat down to listen to them, so this is just a word of caution. If the students show up, you should be ready to inform them instead of convince them. To quote my coach, "It's hard to get 'em in the door. Once they're they see how great it is, but you have to get them there first.".
5) Stay flexible
-Maintaining your flexibility will do worlds for your blood pressure. I do not even pretend to have made a dent on the possibilities to use for recruiting. I have barely listed any concrete steps our team takes to recruit new members. This is mainly because I feel our team works in such a way that to describe recruitment, I'd also need to cover how we plan Ramp Riot, our end of year team celebration, the competition, every aspect of our team. Having said that, I do have more example that I omitted a lot to keep this post to a manageable length.

Michael

P.S. For a more comprehensive coverage of team recruitment, [plug]visit my teams site and request a Team-in-a-Box set[/plug]. Also on that note, if you're interested in contributing material to help us develop an even more holistic outlook of FIRST for our DVD/CD set, PM me, and I can work with you to help coordinate and arrange it so we can put it in the next version.