Elie makes an excellent point. SCORE can help you with this or you can go to Nolo to see what they have, at a reasonable price. If you want to go it alone, there are the critical things that should be in a founders agreement:
This one has a great deal of information but it's a bit hard to read for a start-up noob:
Jarie's answer is a good summary of things to consider. I think what you are referring to (given your request for "vesting language"), however, is a Founder Stock Purchase Agreement which applies to a corporation. The alternative is to have both a Stock Purchase Agreement and a Founder's Agreement. The former is slightly more common. If you decide to form an LLC with partners, you should all of the follow as well but you put it in the company's operating agreement.
Here are several factors that you should always consider in a startup founder's stock purchase agreement:
Some good founder stock purchase agreement templates for a DE corporation I have found thus far. Please go over these with a lawyer.