On the course diagram they will write a "table" on there. It's basically the "rules" of how that class will be ridden and when to do the jump off. Ever notice how in grand prix classes everyone always waits until the end for the jump off? And how in "normal" jumper classes people do the jump off immediately after their round? Different table.
There are a million different tables but I'll list the more popular ones you'll be most likely to see:
**Table II Section 2(b) : What most people think of. You go and do your first round. Any faults you leave the ring. If not you wait until the buzzer goes off. I think you have 45 seconds to make it through the timers to begin your jump off.
**Table II Section 2(c) : You go and do your first round and assuming it's all clear IMMEDIATELY proceed to the jump off. So there are like 15 jumps in a row and you need to know exactly where the cut off for the first round is and where the jump off begins. I've had them do it in the middle of a line before. If you were not clear the buzzer will go off after your last jump of your 1st round to excuse you from the ring. This table is often called "Power and Speed" because when you watch people ride it, they start off slower and more careful and then pick up the pace.
Table II : Prize lists will often refer to these as "blue ribbon classes". Basically if you're double clear, you get a blue ribbon. Personally I think it's kind of dumb, but a good course designer will make a Table II class really challenging so you're not handing out blues left and right.
Table II Section 1 : Timed first round. No jump off. All based on whoever's fastest with the least number of faults. I've only done these a few times. I personally think it's the show manager's way to move things along.
Does that make sense? So you get to your show, look at your course diagram, and at the bottom it says, Table II Section 2 (b). Ah, you immediately know there will be 2 distinct phases between your round and the jump off. There are a million tables (ok, so only like 10) but the main ones you'll see are the top 2 I listed. I've done a blue ribbon class like, once, I've done a Timed First Round a few times... There was one show that was had "Optimal Time" (I forget what table it was). Basically they had a set time everything should be and you got time faults for going over or under that time. If it helps a lot of people use nicknames. More often then not people will use the term "Power and Speed" instead of Table II Section 2 (c), but the course diagram will always use the Table.
Make sense? Sorry that's so long. This is maybe one of the bigger differences in an eq course and a jumper course, learning how to ride each table.