I don't have a pipe club in my area, but I've thought about starting a pipe and cigar club for years. Plenty of great advice listed on the previous pages. I've attended plenty of Pipe Meet Ups (casual gathering of pipe smokers), and what I find works great is...
-Be open and inviting to all, as you all have a common interest in pipes.
-Don't talk politics, religion or other topics that may create hard feelings for others.
-Don't be a pipe snob. If someone only smokes corncobs so be it. No reason to hate on someone else's preferred pipe of choice. Maybe they can't afford a nicer pipe, and you don't want to give the impression that they're not worthy of membership because they don't smoke an expensive pipe.
-Don't be a tobacco snob. If someone prefers aromatics or OTC blends don't hate on their preferred tobacco of choice. Maybe they don't have access to other blends or haven't discovered other blends yet.
-Take some of your favorite tobaccos, and some small sandwich bags and a sharpie pen. Be open to sharing a bowl or even a small amount with other members of the club. Put some in a bag and write the blend name on the bag. Others will be appreciative of your generosity. This is great when you have a hard to find blend that many haven't had a chance to try.
-Feel free to bring some of your favorite pipes, so you can show them off or discuss why they're your favorite. Just remember not to be pretentious about it so you don't discourage others.
-Share your experiences good and bad, or hints that have helped you along the way, or area's that you struggle with. Chances are you'll find someone that has had similar experiences and you may be able to help them with something or they may help you with something.
-Check to see if there is a dress code and try to follow it, but don't discourage those that may show up out of dress code policy. Usually casual or business casual is fine.
-If the club is held at a tobacco shop then its a nice gesture to purchase some tobacco or accessories from the shop.
-Just be yourself. Don't try to be someone you're not. If you don't know a lot don't pretend you do as the experienced individuals will pick up on that and it doesn't make for a good first impression. If the regulars don't take to you at first that's fine. Just keep going and if its a good club the members will welcome you.