Cool. Well I'd recommend making the offering very simple like the example links I included. I've included a sample below (
i-ll-back-your-kickstarter-project-t1418.html)
"I'll back you for $1 and will tweet that I've backed you. However, you must first back my campaign for at least $1 and tweet @_______ that you've backed it (include my project link).
Also, once you back the project come post here telling us you've done so, and include a link to your project so we can all take a look and tell you how awesome you are for being part of a community geared toward helping each other.
I'll then back your project & tweet within 24hrs. (most likely MUCH sooner)."
You can also set a limit to the number of projects you are willing to back (or amount you will spend).
I usually make the topic sticky so that it appears at the top of the forum when someone wants to do this kind of promo and I help promote it