keep at least 3 ideas in your head at any given time. move on the ones that it's easiest to move on. reevaluate where you're at regularly. if you're able to make consistent progress on one idea, just follow it until you run out of easy juice ("juice" meaning "the stuff that comes out when you squeeze your brain out). then decide again what to do next. when deciding, it may help to write out all of the ideas you can think of. and if you've forgotten some, guess they weren't that important anyway and if they pop up again, you'll act on them then.