I'm brand new to motion tracking with AE. I followed the tutorials, set up the two motions of motion. I'm mostly just adding text in, tracked with the background image. However, two things make my clips slightly different:

They're on a jib, so things tend to exit the screen, and the motion isn't perfect

They depth of field is incredibly shallow, so tracking references aren't great because they go out of focus as the camera moves.

I've tried tracking to multiple objects and then realigning the different series of tracking points. It seems like every time, I get some screwup. The text goes sideways, a random point jumps around and I don't know how to change it after setting it up to the text (removing it, changing the values, nothing seems to change the screwup). Is tracking always this crappy?

With shallow depth of field there's only so much you can do. Tracking relies on contrast and pattern recognition. Blurred image makes it pretty difficult. You can experiment by enlarging tracking area or pattern area or both. If all else fails, you're down to correcting tracking points manually. Which unfortunately sometimes needs to be done.

This'll be an interesting thing to look at in CS6. There's a new engine that will generate a "cloud" of tracking points to calculate 3D surfaces. I haven't had a chance to dig deeply enough yet into CS6 to see if they added the same technology to 2D motion tracking but if so, it would go a long way toward solving difficult tracking problems like this.

I'm not sure how to fix tracking points manually AFTER setting the information to the null and then parenting the null to the text. I've tried changing the values numerically but it doesn't do anything, and by looking at the tracking points on the image, they don't look particularly off.

The biggest issue is that I'm trying to have an object come on screen halfway into the shot and the exit screen, tracked with another object (for example, say I had a pan across a keyboard, the letter D was on screen for maybe half the shot, and I wanted to put a word next to the letter D, so it starts off screen, comes in with the letter, and exits screen with the letter). This seems easy enough, but it always idles on screen before the tracking point appears for some reason. I tried tracking to a few different points that come on and off screen at different times, and then lining them up, and that helps, but the text still appears on screen before it should and I can't figure out why.

I've tried finding a Mocha tutorial, too, but every tutorial is for an object that is always on screen and never exits, and adding something that stays on screen.

Here's the video. I'd like to put text next to the stereo, which starts and ends out of frame, and remove the security system logo.

MVI 0136 - YouTube

Try Mocha. It should be perfect. Start in the middle where the stereo is in frame, and then track forwards and backwards. I think you'll get much better results than with standard AE tracker.

As far as manually correcting the tracker, you do it before you apply the tracker to the null object, on the tracked layer. If you hit U, you will see the tracking information. Simply reposition the tracker on the frame, and it's done.

Yeah, Mocha is what you need here.

Yep, chiming in with all the others. Mocha would be the answer here, as it allows you to define a plane and track both forward and backward. It is MUCH more advanced than any internal tracking mechanisms that AE comes native with. I recently started working with it and there are some caveats as to how you need to organize your assets in comps to composite them how you want it, but thats part of the learning curve!

Re: lingering on the edge of the screen...when the bit of image being tracked gets near the frame's edge, the tracker quits on it, dropping the tracking point where it was last seen. So track other items on either side of your desired bit so AE will record enough motion to get your desired item off into the wings. Hopefully your education included parenting nulls together in order to combine tracking data from one mark with another. Another trick to editing trackers: you can transform part or all of the tracked path by selecting the path nodes shown in the comp-preview window and then either arrow-keying or dragging.

Mocha came with cs5 (like a lite version or something) does that also come in cs6?

Yes, and it is integrated so that you can launch it directly from within AE. BTW, the 3D surface engine I mentioned before is a new and separate feature from AE's normal motion tracking, so Mocha may be your best option for tough situations like yours.