I like spray adhesive the best. I use Sullivan's. $10. I've used it for about 8 baby size quilts now and still using it.
I have a Quilter's something basting gun, paid about $29 for it.
I don't like the holes in pokes in the fabric, and I don't like having to baste every four inches. Also, it works better with a basting grid underneath. My back doesn't hold up.
I don't like basting with thread for the same reason. My long arm quilter charges $20 to baste. That's too much to me.
My friend uses the quilting basting safety pins. Same problem with my back.