The first thing would be to figure out what you want to do. Do you want a card trick, coin trick, trick with everyday objects.
Cards: Transposition, Card to wallet (or other impossible location), etc...
Coins: Coins across, one coin effect, etc...
Everyday objects: What object? What do you want to do with it after you pick the object.
If you have a general idea of what you want and criteria it has to meet then you can start thinking about ways to achieve it.
Letting ideas come naturally is a good idea, but you can sit and figure out a method for any problem if you're a puzzle-type of person. Just don't make the effect itself a puzzle for your audience, make it magic.
