After you fire the 2nd shot, break the action open and keep the muzzle pointed down and return the shotgun to the stand. Between stations, always keep the action open and do not load shells until you are at the next station stand and it’s your turn to shoot.
Assuming you have removable choke tubes, DO NOT bring them with you on the course. Pick a fairly open matching set and install them before you start shooting (preferably at home before you leave for the event). Modified is usually a safe bet for this type of event.
If you're truly a newbie, and this event has shotguns at each station, I would be using as many different types as are available. This is a perfect opportunity to see what's out there and try it. Especially if you plan to continue shooting clays ... a coach gun isn't an ideal clays gun.
Swing until you are ahead of the clay and keep the gun moving as you squeeze the trigger!! If it is going away from you get ahead and slightly below. Keep the gun moving!! I have to constantly remind myself to not stop when I squeeze the trigger.
How long is the barrel on the coach gun? Everyone and every gun is different, but I don't shoot nearly as well with my side by side as I do with my O/U. I shoot best with my good old Mossberg 500.
As others have said, a coach gun might get style points, but its not ideal. If they have loaners, use theirs. They are probably better set up for it. Thats what I did. My O/U didnt leave my trunk.
Also like others have said. Lead it and dont stop moving just because you pulled the trigger. Keep following it until the clay goes poof. Many shots are missed because they stopped following the target and ended up putting shot behind it.