I'm actually lucky enough to be currently attending my "ideal Church". It look a lot of looking and searching, but I found it not too far from where I live.
There are a few things that I looked for.
The foremost was children's programs. My kids LOVE going to a good Sunday school. It makes me laugh at how they BEG to go back the next week. So different from how I was raised.
Second was community and charitable involvement. The Church can be one of the most powerful social charity organizations around. I am so proud to be a part of a Church that gives it's time, money, support and effort into causes not only local but worldwide.
And then also important to me, as someone still discovering their belief system, was roundtable bible studies. Where you aren't being preached at or expected to regurgitate information from a book, but actual bible discussions with different perspectives encouraged and discussed.
That's a few of the major things I look for... on top of a general feeling of warmth and welcome. That probably even tops my list!