When pairing up seams, make sure that they are going in opposite directions, and that when you feel the seam, it feels flat. What you can do is then very carefully pin on either side of the seam, making sure it stays put. Then sew about 5 stitches over just the seam. Then you can check to make sure that it is right. Doing it this way until you are more proficient, will keep you from ripping out the whole length of the row. If it's lined up, go back and sew the row. No need to rip the 5 stitches out.
I learned this from a friend several years ago and it has saved me lots of ripping. But the more you quilt, the better you will get at matching seams.
Another tip is when you are sewing patches together, make sure the seam on top is going up, or toward the machine and the bottom seam is going down, or towards you. This will make the feed dogs push the seams together. I hope this helps you. Good luck. Gina