DJ Techtools Ean Golden explain how to beatgrid your tracks.
It's like laundry. Do it every day and it gets done. Do it rarely and it's a hell of an undertaking.
What's explained in the video is the best way to do this, but when you're playing a gig you can do it then and there.
When you're playing a gig the sync type is sat to Temposync.
If you see in the video when Ean goes off beat the phase meter above shows the offbeat. But when you've got a track that is not beatgridded properly it will show off beat when you've got it in sync. When it's all matched up in your ears you can use the move grid to move it untill your phasemeter is correct.