I also agree with the others. Its too early to write letters. I also think visiting some campuses and going to some games is a great idea at this time.
I think the next 1.5-2 years is a great time to focus completely on raising your game as much as you can. Make sure you make your HS team and earn a starting spot. Get on the very best summer team you can...one that will challenge you to get better in order to play and compete against good opponents. Hone your hitting and/or pitching skills.
And make sure you get off to a good start academically in HS. That now matters about as much as anything especially now that Spring is approaching and practices and games will take away 2-4 hours a day of study time.
Good luck!