You seem like you're really well prepared, and really ahead of time. Just in terms of other hints, aside from the research/posters thing.
1. Good GRE scores...study, study study.
2. Terrific letters of recommendation. It sounds like you're already working with professors, which is great. If you need more, start now, and go into someone's office hours and talk with them. Professors loooove to talk about their work, and it's a great way to make an impression.
3. In the fall, try and send emails to people you're interested in working with, and ask if they're taking students. Don't ask a million questions, but just see if you can get the info. I'm in a clinical program now, and it definitely helped me eliminate a school or two because at other schools, a professor was going on sabbatical, and wasn't taking students. I know a couple of friends who got their hopes up about a school only to find out the person was never taking anyone.
4. While reputation of the school is important, Match with research you're interested in, and the professor's reputation is more important.
5. Lastly, be open to what you might like! Look around, and really explore the programs. I have to say, prior to interviewing here, I didn't expect that I would love my program the way I did. I sort of surprised myself by it being my first choice!