Lorli,
When I'm doing straight line quilting and having problems with tension, it usually means that I'm trying to sew too fast or the needle isn't the right type for what I'm sewing. Always be sure that the bobbin is wound evenly, placed in the machine correctly and that everything is threaded right. Your quilt sandwich has to be supported all around so its not falling off the table.
I prefer Superior top stitch needles in sizes 90/14 or 100/16. I've been machine quilting for 25 years and learned so much. I use the "Machingers" gloves, it helps me have more control over the quilt sandwich.
When you're having problems with puckers,tucks and such; feed the quilt toward the presser foot to help ease in the poofy areas. If you're using a poly batting it has to be very well basted(2-3"apart) or it'll slip and slide everywhere. I like an 80/20 or 100% cotton batting as it will stick to your cotton fabrics and reduce puckers.
Machine quilting requires much practice, so be patient with yourself. Relax your shoulders, take frequent breaks. I quilt for about a 1/2 hour at a time and then go do something else and then come back to it.
Sharon in Texas