1) Bypass the free design sites or you will get what everyone else has. A membership tribal design site highlights designs by artist that specialize in tribal body art. They know what types of tribal designs look good where and with what elements.
2) Use a tattoo artist that specializes in tribal body art. If you are going with tribal art you need a professional who knows what they are doing and has done it before.
3) Go to a tattoo parlor that adheres to the proper industry health and safety regulations. Things can get nasty quick if you go to a tattoo parlor that is more concerned about making a quick dollar than the proper business and health practices. Your membership site posts reviews of different tattoo studios and what health and safety practices you should look out for.
Good luck getting your new tribal swallow tattoo!