any preference on which area/state/school you want to do internship at? first, make a list of schools you want to do internship at, then go to their website, look for headings like research or something similar and read about their internship program. the first thing you should read is eligibility  section because a lot of schools don't take international students. if everything looks fine, send an email to the program coordinator asking what kind of projects they are planning for upcoming summer and mention your interest too. see if they have anything you'd like to do. if everything looks good, promote that school on the list. your final list should have 6-7 schools at least. start asking  for recommendation letters NOW, applications for most of the schools are due in before the first week of february. so, plan accordingly.

 here's a database with collections of internship programs. there are several others, but i found this one quite helpful. http://people.rit.edu/gtfsbi/Symp/summer.htm#skip