First and foremost you need to look at all ways to fund your start-up not just outside investment. How far can you bootstrap your start-up and self fund? Are their ways to get your first clients to fund development for in return for free life-time use etc. If this is not possible then you move through the different avenues of funding - Owner funding (how much can you put in - Outside investor look favorably on an owner having skin in the game), friends and family, angel investor, VC etc. I did not put crowd funding within the list as I would consider that more friends and family just organized through a kickstarter type site.
The second thing to consider a compelling story on how the funding will be deployed to grow the company and to what level. From David Rose's book on angel investing; a typical angel will be looking for 25% IRR for their entire portfolio (Or in simple terms a 3.8x return on their investment on a 6 year hold period). In a portfolio of 10 companies 5 will fail on average, 2 will return 1x, 2 will return 3x which means that the final one will need to return 30x to make the angel's desired return. If that is the case any of the 10 need the POTENTIAL to make 30x return. How and to what degree can you offer returns for your potential investor.
Without knowing the details about your start-up (sector / timelines / team / product or service) it is tough to give a concrete answer. But here are some good rules of thumb.
1) Know your story
Before any investor comes on board, you need a clear story to tell. What is your big idea and how does capital get you there?
2) Demonstrate traction
Proving that your product / service is successful on a smaller scale is a must have. A start-up without any traction is too dangerous for an investor and not interesting enough for crowdfunding.
If you would like to talk in more detail about how to tell a convincing story, or to demonstrate traction, give me a call.