Basics Rules of the Road
There is a whole book on the rules of racing but I reckon there are only 3 you need to know. Generally at GMSC if you are inexperienced, the other sailors will gently point out the error of your ways if you are wrong. If you have any doubts have a word with a member of the sailing committee or one of the more experienced sailors who will be happy to help you.
Rule 1. Port/Starboard
Basically when you are tacking, often on the way to the first mark, if you are on Starboard you have right of way. I remember this one as "If you are sitting on the right of the boat, you're alright". This same rule applies for example two boats running downwind.
Rule 2. The windward boat gives way.
If two boats are on the same tack, the boat closer to the wind gives way. There are a few variations that the leading sailors get excited about (they will mutter complex things about overlaps and sailing your proper course), but just remember the basic bit. In the picture, the white boat is the windward boat and has to give way.
Rule 3. Rounding a mark
This one gets a bit more complex. When you are coming up to a mark when you get to 3 boat lengths from the mark, any boat that has got an overlap (i.e. the front of their boat is ahead of the rear of your boat) has to be given room to go round the mark. They will normally shout "water at the mark" or something like that. If they clearly have no water and are trying it on shout back "no water". But in the early stages, it's probably wise to give them room. In this case, the blue boat needs to give the purple boat room to go about the mark including room to turn towards the next mark!)
What happens if you get it wrong? The main rule is to avoid contact with another boat. If the other boat has to take avoiding action because you have broken a rule, you will need to do a 720-degree turn i.e. go round twice. It's easier to bear away and start with a gybe. You will know when you have to do this because the other boat will be bellowing at you to do your turns. If you accidentally touch a mark, then you do a 360-degree (once round) turn sometime after the mark but before the next mark.
Click here to view a YouTube RYA video
Learn about the rules of racing
Ever been in a situation where you think you are in the right but not sure? Have you been carved up by one of the experienced sailors but not felt you know the rules well enough to protest?
Two pieces of advice
1. No one minds a protest it's a good way to find out who was wrong, so speak to the race officer if you are not sure for some guidance. Don't just let it go, as at a minimum they will be able to explain the situation and who was in the right so you can learn.
2. Learn a few more of the key rules. There are some great books on the rules don't get a copy of the rules, but a book on the key situations
Why not have a go at this quiz it contains the key situations and will let you practice and learn