I strongly advise you shoot the "fun" class if they have it for your first time�just to become familiar with how it is done. It would be better if you also shot with someone that has done it before.
The hardest part is learning to shoot to score, and how to judge yards.
As far as scoring: hit any part of the target and it is 5pts., then the 8-ring, 10-ring and the lower 12-ring. You can call the upper 12-ring but the lower 12-ring will not be in play if you call the upper. Additionally, if you touch the outside line of a ring, even by a hair, you get the higher point value. Here is a practice target of the ASA rings.
The best thing to do is to aim for the IBO 11-ring, a lot of shooters aim for the bottom 1/3rd of that ring. The thought behind that is, if you are off a little your arrow will still fall somewhere into the 10-ring and you may even catch a "lucky" 12. There are also times when lets say the target is 33yds you will put your 30yd pin in the center of the IBO 11-ring and let the arrow fall into the top 1/3rd of the twelve ring, or at worse you still have a 10. Shooting even (a round of 10's) is a good thing, and in a lot of classes at the amateur level that will put you near the top of your class.
Since you mentioned the hunter class, that class is half-known and half-unknown�you need to learn how to judge yardage. What I see works best for most is to learn how to judge 10yds. The easiest way to describe it on here is learn 10yds and let it burn into your brain�where you can nail a 10yd distance anywhere. Then you measure your shot, 10yds at a time.
Lets say the target is 34yds, that will be the average distance at a course that is setup properly for your class, First, you find your 10yd mark, then add 10 to that and then 10 to that (your at 30yds now)�this is where it's going to get kind of tricky. You know the target is further than 30 but closer than 40, so you find your 30yd line and measure half of that to 35yds. Is the target closer than 35yds or over 35yds. It is closer than 35yds, so now you know it is closer to 35 than it is 30 so you find the mark that is roughly 32.5yds and figure if it is closer or further from that. That process will generally put you within a yard or two (.20"-.35") from the actual distance. Judging yardage takes some practice, but it can be done anywhere: the grocery store, your yard, the woods, a parking lot, etc... and I recommend you become very good friends with your range finder and practice judging yardage, in all kinds of terrain (flat, hills, dips, behind trees, etc...) as much as you do shooting your bow�if not more.
That is why I suggested the fun class, so it can be all known yardage, if that's what you want to do, and you can practice estimating before you range it, you will find that you are often very off (5-10yds) the first few times you do it.
A couple of random pointers is if the club you are shooting at uses the ASA McKenzie style targets and you cannot see the rings for whatever reason, the area to shoot at is straight up the back of the leg into the middle of the chest. The "line", up the back of the leg, often will come near to bisecting the 10-ring. Another hint is make use of other shooter's nocks as a reference. It happens often where someone is either just barely above the 12-ring and the target is 33yds, you settle your 30yd pin on their nock and you land just below them in the top of the twelve. However, get ready because someone is fixing to do it to you as well.
Finally, if it is sunny or you have shadows or marks on the target, use them as reference points. Unless you have eagle eyes, you will not be able to see the rings from the stake through your peep sight. That is why we use binoculars to find reference points as a guide where to shoot and what to aim for. A shadow from a limb, a shot out area in the target, a dark or a light spot on the target, painted features of the target or a arrow nock all make good reference points to guide you where you want to aim.
I'm sure someone can add to this, but it's 2am and I'm tired.
Good luck and keep the questions coming if you have them and someone may have the answer.