Randy,
Look for the longest track record with consistant earnings (c/c and/or IRR depending on your goals). Sean Cook/Paul Kaseburg says this is the absolute biggest thing you can do.
Think about it, all proformas are 'guesses or stories about the future'. The only thing that investors care about is their returns. I know, past performance is no indicator of future performance. However Buffett and Munger have always said, they buy companies that have very long term solid track records (predictability) that are on sale. I want my operator to have gone through the last recession. There is amazing wisdom that is gleamed only from time. I have spoken to over 300 operators or their investor relationship department and I am amazed the the huge difference that I see and hear from those that have been around the longest.
I hope this helps. Syndication is like getting into any other area of RE investing. It is NOT passive. You must read, study, and think to get the most benifit. Start with those books. If you don't have much time bet Brian's and listen to the audio while driving, walking, working out etc. You will be amazed at what you learn.