I'm far from skilled, so take this lightly!
I was taught to try to get an anchor stitching in, in the middle, so I'll sew from top to bottom in the centre, and again from left to right, in the centre of the side.
Of course, this is approx, and depends on what type of quilting you are doing.
And if a larger quilt ... more anchoring.
Then continue on working from centre down and centre up, etc.
Others? agree? or not?