Comment You probably need more info to start with. (Score 2) 292
For sites like Ancestry.com, you really need to have a good few generations (4-5, minimum) to start getting good results back, since quite a bit of it is crowd-sourced links from distant relatives. Even at that point, there are a few points in history where the records / links just suck, and it usually takes quite a bit of digging to find another link. Over the course of roughly a month, and with some good spots of luck, we were able to trace back several lines of my family through Ancestry.com, and other sources for several hundred years.
Fortunately, there's a standard file format for genealogy data, and Ancestry (and other sites) usually support exporting to it.
Unfortunately, my data yielded a genealogy chart that most of the current open source or free software couldn't render very well. I've been considering writing one myself, that at the very least could render out multiple pages at once for printing, rather than manually forcing the user to set things up correctly for each sub-branch...