I'm slow and methodical, so I x most negatives, until I get to the point that I'm moving known positives from the bottom to the top. If I have all the positives in second and third squares down the left, I don't finish second down on the right. You'll know after a while when you have enough info to have all the answers and it's safe to skip some x's.
If you have access to more than one computer, try them all, it makes a big difference. Some just react faster and smoother. Screen shape changes it. With some screens, not all clues fit on the screen and you have to scroll down. Personally, I do better if I take my time because then I don't make mistakes and have to start over.
Interuptions and distractions are my biggest problem.