The quick answer is that motion tracking is tough...and given enough time around it you tend to get a sense for what features will track well and which ones won't. Sometimes hand tracking (at least a portion of the shot) is the only answer.
In the mean time, I'd suggest you check out Eran Stern's tutorial, "
a walk in the park" to address some of your out of screen difficulties. I'd also suggest taking a look at Mocha for After Effects if you foresee yourself doing a lot of tracking work - it's really spoiled me.
Carl Larsen
TelescopeMediaGroup.net
