Coming up with ideas is hard, but you can do it, if you follow these tips.
1. Come up with ideas every day
Spend half an hour a day writing down ideas. At first the ideas are going to be pretty bad, but you will get better.
Stealing ideas is OK. Everybody does it from Bill Gates to Bill Clinton. If you see a good idea somewhere, start thinking how to make something like that of your own.
3. Start working on a problem
If you are working on a problem, you mind will subconsciously try to solve it. This is, where the best ideas come from. You just need to spend some conscious effort on solving the problem everyday. It's not difficult to find problems in need of a solution. Just think of something that annoys or bothers you.
I was planning on writing more, but this is all you really need. If you follow these steps, after a while you will have tons of great ideas for a business.