As for frequency, head out to the field and take notes. Visit the field you figure you'll fly at most often, when you figure to be flying there. Walk over to the frequency board and write down all the channels in use. Do that a couple of times and you know what channels NOT to order for your new radio. This is a very worthwhile thing to do. Once you've got the list, you might or might not then walk around and ask the flyers what other channels they fly frequently. You get to know some of them this way, and you might discover a frequency or two that is troublesome at that field and would be worth avoiding.

While you're there, watch and see who the modelers are that everyone gets to help with problems. This isn't a trivial matter. It's really worth taking the time. And when you have questions, wait for one of those guys to be standing around and go ask. You'd be surprised how the quality of help differs from modeler to modeler. And you'll know from observation who at the field likes to help and who is most worthwhile getting help from.