Go out and meet people. Talk about your ideas, and for gods sake, listen for theirs. Share your passion. Don't be afraid of someone else stealing your idea. There is more to an idea then just "implementing" it.

Stop reading all the startup blogs. IMO, that's mostly wasted time. Spend this time doing things you love, step out of your comfort zone and try something new (e.g. hobby). Maybe you'll find out that your "startup idea" is an interactive online climbing guide.

Source: I'm 23.