Learning how to be safe out in the surf will insure you years of enjoyment and keep you free of hassles from the other surfers in the water. The main issue here is safety. Surfboards can be potentially dangerous if they come in contact with another rider or yourself. In other words, when they hit you, they really hurt.
Good surfing waves have a peak, somewhere in the middle of the wave usually. This is the part of the wave that will break first and is the steepest part of the forming wave. The paddler closest to this peak has the right to the wave. Because we always surf away from the peak and the whitewater, where the peak is will dictate which way to go on the wave (left or right).
If another surfer is paddling for the wave and is closer to the peak, it is his wave. If you drop in on him and he runs you over, it´s your fault. So do not "drop in" on people. It shows poor form and is potentially very dangerous. It can also seem to be a show of disrespect to another individual. This can create a problem.
When paddling out, if you must get over a wave that someone is riding, paddle behind them (on the white water side). This generally means getting stuffed for the sake of someone else's ride. Do not paddle in front of someone unless you are so sure that you will be 20 feet in front of them.
Do not surf in a big crowd or you are inviting trouble for yourself. Beginners do not need the best shaped, perfect wave anyway. The problem is this: all of the great surf spots are not a secret anymore and they are already overtaxed by surfers that have bonded with these places. If you go out there and start making mistakes, it can get ugly. The other breaks down the beach away from the shredders will be just fine and you can still enjoy the pure joy of surfing with just your friends, or even all by yourself.