Usually companies are valued by some multiple of something -- often $sales, sometimes inventory, sometimes registered users, etc. Knowing nothing about your company, let's value it at 3x sales, which is kind of in the middle of the road (sales is a reasonable metric for a B2B product company; most B2C online product companies use users; a service company will use a lower multiple).
So what will your sales be? (Or users, or inventory, etc.)
Don't even try to raise money until you can answer that question in some reasonable way.
Hopefully your research has given you some reason to think you can answer this. If not, do more research.
Then, as fm says, you need to know how much it'll take to get you started. That'll tell you who you need to ask for money. Need $$$millions? VC. $$$hundred thousands? Angel. $$$ten thousands? Friends and family. If you fall in the third group, then mostly you want to ask for something that your friends and family will be comfortable taking, since they mostly want to help you. Value your company so that it works out right and is vaguely defensible by the metrics above. If you fall in the second, don't worry, the Angel won't try to take too much, use the same valuation. If you're in the first... then you need a lawyer.