I have quilted a long time and basting my quilt sandwich is my least favourite part. I like Hobbs fusible 80/20 batt and iron the sandwich flat out on my old carpet in the basement. I also like basting with 505 soray but that I have to do outside because of the smell. There are some longarm machine quilters that will baste your quilt at a charge or you can have your quilt quilted by them. This is called quilting by check.
I usually pick a patterned backing as this hides most quilting errors. I quilt from the center outward to the quilt edges so any excess backing fabric gets moved to the edge. As others have said, do some smaller practice pieces and you will get better.