For SITD, I use a foot that has a blade/guide in the center to help keep me on track - on my machine I have a built-in walking foot so I can use that blade/guide foot with the walking foot; you may have to pick between a walking foot or a non-walking blade foot; experiment to see what works best for you! I usually set my needle so it's just to the side of the seam, but sometimes I go for the seam itself. (I always miss my mark in some spots no matter what but that's OK, I quilt for family and friends and they'll never notice. And each quilt is just a little bit better than the last!)
Main thing, I think, is don't be afraid or dismayed by mistakes or by needing to go slow. I see some of these videos of people doing beautiful quilting at 100 miles an hour and they make it look effortless...these are people who have practiced a LOT. It's kind of awkward to manage the quilt fabric and you're bound to screw up a lot on your first couple of quilts so be ready for that and don't worry if you're not instantly an expert. Keep at it and you'll keep getting better and better.
I second (or third) the quilting gloves...they really do make a BIG difference for me. I've tried the "halo", I've tried rubbery fingertip covers, I've tried hand-held grippers and for me gloves work the best by far, but you should experiment with that as much as possible too. You can buy quilting gloves (and I do love my Machingers) but any gloves with grippy fingers will work, like gardening or mechanic's gloves.
I used to dread quilting because I was sure I was about to ruin each quilt at that stage, but now I'm finding it's becoming one of my favorite parts of the process! I'm still pretty bad at FMQ but gosh it's fun to do!
Making yourself a nice new set of potholders is a great way to practice quilting, by the way.
