I have been messing around with the calibration and have a few tips:
1. Go into the calibration tool and reset the pen calibration if you have already adjusted it.
2. Start the calibration. The first time you calibrate, there is a more detailed (16-point) "major" calibration. For this part, view the tablet from directly above, and hold the pen straight up-and-down (perpendicular to the screen). Tap all 16 targets.
3. Test the pen. I use one note with line rulings and try to trace the lines, and write directly on the lines.
4. It probably won't be right yet, now go into the calibration tool again. This time there will be only a minor calibration of 4 points. For this calibration, hold the stylus as you naturally would and tap all 4 targets.
5. If there is still weirdness, you can repeat the minor calibration, and hit the targets intentionally off center to compensate. Doing this last part will require some trial and error to get it perfect.
I have improved over the default using this method, but there are still some edge and corner issues. Overall it is better than the default, but if you still have problems the default is not bad. What they really need is a more thorough calibration that will have some targets near the center. Hopefully they will improve the tool. Hope it helps