Well, you might talk to the professors in whose reseach you're interested in, and ask if they have RA funding for your first summer. You don't want to go somewhere to study cosmology only to find out that the cosmologists can't fund you your first summer (well you can, you'll just have to be a summer TA). Also, see if you can get the preparation materials for each school's PhD qualifier. Most schools give you a "free shot" your first summer, in which you can take the qualifier without any penalty if you fail. If you study hard, getting this beast out of the way before you even start grad school will be a HUGE load off.