Hi John,
I think most fishkeepers alternate between flake and a couple other things to give the fish some variety. That's what I do. In addition to flake, your LFS should stock freeze-dried food (e.g. bloodworms, tubifex, daphnia, brine shrimp) as well as frozen food (e.g. bloodworms, glassworms, daphnia, brine shrimp). Then there are other "staple" foods that are essentially the same things as flake but in a different form (like tiny "crisps", or "crumbles", or wafers). I even keep three kinds of flake for variety. My fish eat better than I do.
I feed once per day. Here's an example rotation I might do:
Day 1: Frozen daphnia
Day 2: Flake #1
Day 3: Frozen brine shrimp
Day 4: Flake #2
Day 5: Freeze-dried tubifex
Day 6: Flake #3
Day 7: Frozen glassworms
Day 8: Sinking "crumbles"
Day 9: Start again!
That gives you an idea. Not everybody uses so many different kinds of food, but personally I think your fish do better if you'll alternate between at least two or three from time to time. And don't forget the bottom feeders! You may need to add special food for them if they don't end up with some of what you put in for the others.
Basically, you're right about the frozen food. It has to stay in the freezer (obviously). But it's not as bad as it sounds. It generally comes in a Ziploc-style bag that closes or individual blocks of the food are packaged so that you only "punch one out" of the packaging when you're going to feed it. I reserve one small shelf in the door of my upright freezer for fish food. It doesn't have to "touch" my other food. To prepare for serving frozen food I dip about 4 fluid ounces of tank water from the aquarium and put the frozen food in it. Let it sit a few minutes to thaw, and put it back in the tank. Fish will attack it! Just remember: never, ever thaw frozen food in tap water - only tank water.
Some folks give their fish blanched vegetables from time to time. Cucumber is popular, as is zuchini. I've tried it with my fish a few times with mixed success. They don't seem that crazy about it. Someone who has more success with that should elaborate better than I about it.
Hope that helps.
pendragon!