One way to begin thinking about stocking is to take a little sheet of paper or notepad with you as you slowly look over the tanks at the various LFSs you can get to. It can make you feel a little self-conscious but you can always just be honest and say you are trying to work on the stocking plan for a tank if someone questions what you are doing. Meanwhile you want to be capturing the names of fish you like and don't like based on what you see.
Just the act of doing it will also help you to formulate beginnings of plans in your head which is good too. Then you come back and test some of these plans and some of the species you now think you might want against the members here. Lot's of the fish may be totally inappropriate but that's ok, that buys you some experience and you should be sure to capture that for yourself too. You never know when you'll want to come back to the information you've had interactions about!
Stocking needs a layered approach. You need to keep combing through your different plans an revising them. There's the overall level to not overstock the tank. There are the species that need minimum numbers in order to be comfortable. There are the species that need long swimming space or minimum tank height. There are the species that like particular water types. There are the between-species interactions (that one's huge of course).. there are the considerations of what will swim where. There are colors that go together or don't. There are species that change personality as they grow old. There are species that are prolific breeders and will mess up your balanced bioload. There are species that will help you feel peaceful when you look at your tank. There are species that will keep you from getting bored when you look at your tank.
And finally, there's of course just the getting on with it and not worrying -too- much, lol! It's a trade-off. Each time you plan and stock a tank you draw on your previous experience and it often gives you more patience to draw up a better plan - it's all part of the fun.
~~waterdrop~~