i use colonial knots in place of french knots in my work. i find them to be easier to make than french knots, and for me, colonial knots produce neater results.
knots are all about having the right tension -- you want to keep even tension on your floss as you complete the stitch. once you have a feel for it, you can experiment with looser, loopier knots to create a shaggy area of fill stitches.
you can also vary the size of the knot. to make bigger knots, you can use more strands of floss, or wrap the floss an extra time around the needle.
most importantly, practice! soon you’ll love knots.