You should try AngelList And here are two useful blog articles if you're just starting out
Do some research on your potential investors first.
Check that they invest in companies in your sector and around the dollar amount you are looking for.
Then find someone you both know that can give you an introduction.
Then start talking
Try seeing if you are connected to them through LinkedIn in anyway. I just found out yesterday some of the biggest local angels I have connections through people I work with right now.
Blind-fire e-mails will generate a very low success rate.
It depends if you are looking for just money or for the value investors may add.
If you are looking for value add, then you have to target who you are after. Figure out who can help you most, then you want the strongest connection you can get in the following order:
When sending emails: