there are several ways to join the tails and various tutorials to show one how. i have made at least 50 sets of potholders this year and i practice various techniques on them such as seam joining, fmq, gluing binding, mitered corners, quilting stitching, etc. i have had plenty of practice so i am perfecting that skill. i would say research the various seam joining techniques and find one that works best for you. my mitered corners are turning out just about perfect (one may get outta whack every so often). practice makes perfect.
hutch farm find something small that you can work on (such as potholders, mug rugs) to help you find the technique that works best for you. then keep making them until you feel comfortable with your skill. browse online and find a few tutorials for information and to help you practice. you will be a pro in no time at all.