Right now only StargateHero.NET has Regional Teams so this only relates to that site only.

Once you find out which Regional Team covers the area that you live or spend most of your time in, post in that team's public area and introduce yourself. You should also contact the Team Leader of that Region and let him/her know that you would like to join up. There is a short questioner to get information that the teams need to collect and then the Team Leader will let you know the password to the Team's Private Forums. Please do not share this password outside of your team.

Currently there is a costume requirement to become a full member of a Regional Team, but it is not required to have one to join a Regional Team. You actually have six-months to work toward completing an acceptable costume for membership. If however you do not met that deadline, your Team Leader can grant you another six-month extension. See the FAQ on Acceptable Costumes for Regional Team Requirements. Basically it has to be a recognizable Stargate related costume which looks at least 80% correct at 20 feet away. The "20-foot rule" is one that Hollywood uses for Background costumes and props. That is fairly easy to do, even on a budget.