How Do You Make Sure You Get Paid For Bird Dogging
I am new so I am still learning so forgive me when I ask stupid questions. But how do you know you will be paid for your lead after the investor closes on the deal? Do you make them sign an agreement that they will pay a finders fee? Also do you make the price or does the investor? Thanks............. 
You sign a contract like you said, and you or the investor can set the amount.
In addition to what nebulousd said, I would also say that agreements are only as good as the people who make them. So choose your people carefully. Unfortunately, some people might focus only on the short-run gain (not living up to their agreement with you and keeping more of the profit) and not see the long-term loss (you'll never bring them properties again).
Y'now,
I either assign a contract for sale or just turn the investment peospect over to one of the investors in my group and we agree on a hand or "phone shake"... I have a ton of investment prospects and if they don't pay - they don't get to play. Honestly, I work with a group of good, honest people whose word is their bond. Old fashioned, yes?
C-