Look for a shop with a good reputation, maybe one where you’d want to work in the future. Many employ artists based on their style. It may work if they specialise in a style you excel at, but if you have a style or skill that they do not cover. However, please don’t get too worked up over it. Look for reputable, professional shops that do a lot of business.
Please do not call, text, or email. Instead, go to a tattoo shop, introduce yourself, and ask if they would review your portfolio. Pay attention to any advice they have for you. If they don’t, leave a card and return another time. Make an effort to be friendly, professional, courteous, and mindful of their time.