It's the first two loops that are both the hardest to get right, and the most important. If you don't get those right, you'll never get the rest of the net even.
Pay very close attention to the direction and placement of the twine as you go around the gauge stick. It's down over the stick, then up behind the stick, and through the loop from the back to form the next loop. This is the easiest way to achieve a consistent mesh size.
When pinching the twine to tie the knot, make sure that the working end (that you're going to tie the knot with) lies between thumb and forefinger - I really had to work at this, as it seems more natural to have it under the thumb for some reason.