It is important to find a club that is open to all breeds. If they raise their eyebrows because you have a Doberman, you may want to move on - unless your dog is so good that after the first bite, the GSD people all change their minds
Very important, only work with people that are actively competing and titling their dogs themselves. I learned this lesson the hard way. You learn nothing from people that have been watching the sport from the sidelines and read the rulebook a few year ago.
I would not even take my dog the first time I go out, so that you have plenty of time to observe and socialize. Are people supportive of one another or are they bickering and backstabbing and constantly talking about one another behind people's backs? Are they actually training their dogs or are they sitting around socializing all evening? You will get a feel for that very quickly.
As has been mentioned before, the helpers are very important. You may not know initially what to look for. A good trial helper is not necessarily a good training helper. Teaching helpers (the ones that train other helpers) are usually good, but even there, training methods differ quite a bit.
It all depends on your level of comfort. But just because you are starting out, don't accept anything blindly. If it feels wrong, it probably is. Good luck!