Find a good hair stylist who can style and cut the wig to fit your face head etc. I've purchased several wigs on line and they all needed some styling and cutting to make them look just right.
I would recommend going somewhere that specializes in supplies for cancer patients if there is one close to you. That is what I did and have been very satisfied with my wig purchase. It also helps to find a good hairdresser who is experienced in working with and cutting wigs.
Get a "gripper" - TLC catalog online carries them. They are a must so that wig doesn't shift on your bald head.
I bought all of mine in wig stores. They fitted them there. I needed help,picking them out.
Check out the tlc.org.... They tell you on this site how to measure for your wigs. I used them when I ordered my wigs ,which fit well. You can also adjust the strap like you would on a bra so to speak. They are nice wigs and vary in price