For those that have been around a while these are not a problem but for anyone new, here they are.
~ Check egos at the door.
This place is all about enjoying the hobby. There are builders of all skill levels here and as long as they are enjoying the build, that makes it the perfect build. Critiquing is often asked though and in that case give it like you would want to receive it.
~ Keep it clean.
One of the biggest thrills in this hobby is getting kids involved. Act like you would with a group of Cub Scouts taking a tour of your firehouse, not like 2 am after a fire.
~ No religious or political discussions.
Plenty of other boards for that and no one is going to change any ones mind so it is not worth the grudges.
That's pretty much the ground rules. Follow those and everyone can be happy.