Set it and forget it.
The problem that generally occurs when you think about your intention a lot is that you often end up thinking about how you don't have it yet, and that is exactly what you will get!
You don't necessarily need to act either. It depends on the intention. Just recently I decided to set an intention strictly for fun. I used ALG's suggestion of repeating it over and over as I was falling asleep. The intention - a wonderful surprise. And not just any old mediocre ho-hum surprise, but a HUGE, exciting, knock-my-socks-off surprise! Not something I could act on because I don't know what it will be, so what could I do? Yesterday, the surprise was revealed to me, and it is a doozy. I don't want to talk about it yet because it's still manifesting, but omigod, the Universe definitely delivered. It will be my biggest and best manifestation to date!