Good points DHMom and I'll add to your list ....
5) Be aware of how you are moving the quilt as you stitch. I have caught myself letting it somewhat jump and thus creating that longer stitch. Is your table top smooth/slippery? I clean and polish it up good before I start FMQing, and if it is a longer project, repeat as needed.
6) Check is it a "long" stitch" or one being caused by the top/bottom threads not meeting/catching. Might be time for a new needle. Or it could be you need a different size and/or type of needle.
7) Drag can be created not just by the quilt hanging off the edge of the table, but also, with how you have it sitting or puddled on the table top. Watch you aren't catching it on the corner or even with the way it flops over the front towards you.
8) Echoing DHMom's #1)+#2), for me I find I need to sit a little higher when FMQing than when I am piecing. A good adjustable chair is worth the extra cost.
And as we all, already know ...... practice practice practice!
And if you are like me ... I hate that word ... I want perfection immediately! So instead of outright practice toss aways, one of the things I have done is to make squares for my practice pieces that will eventually become QAYG quilt. Some make dozens of placemats ... and there are lots more possibilities!
Keep at it ... you're probably doing better than you give yourself credit for.