Everyone has a different approach. It is up to you. At some point you have to give potential investors your plan. If you have a general chat with a potential investor first you may be able to guage if you want him as an investor or not.

2 words. Shark tank.

I want to approach potential investors and I need them to fund my business idea. I am in the process of writing up a thorough business plan. Do I go straight to the point and tell them about what I plan to do and what I need from them, do I have to present my proposal to them on the first day that I ask them for help, or do I invite them for dinner for no specific reason or "to talk business" and then present it to them?

I have absolutely no idea how to do this in the most appropriate and acceptable manner. Some of these potential investors are people I already know, but I also want to try approaching people I have never met yet but are known to invest.