Art gives good advice and any further info at this juncture will only augment his input. Nevertheless, I strongly suggest that you buy a pair of clear shooter's glasses with the nylon keeper strap thing. Mine are from Remington. They are the plastic wrap around version with a selection of interchangable lenses and the nylon keeper strap. It cost $20.00 + tax at Wal-Mart.
Next, determine a zone of fire for each shooter. If a bird crosses your zone, shoot it only if you are positive beyond all doubt. If there is any doubt at all, let it go.
Consider your vision and walking as a subconscious activity. Do you think about every movement and glance made when driving or riding a bike? No. Likewise, the same holds true for bird hunting. Just as you glance at all angles constantly when driving, do the same when hunting. Remember, you are not walking, you are covering ground.
Always make sure you and your partners are walking in a straight line. Never lag behind or get ahead. Make sure muzzles are kept IN THE AIR WHEN HUNTING WITH OTHERS until the time to shoot. Watch others. If they are swinging the muzzle around so that if the shotgun fired someone would get there guts shot out, warn them once sternly and if they don't stop, get away from them even if it means walking out of the field and going home.
The guys on the end will usually have a greater fire zone while those in the middle will have a more restricted field. On common technique is called blocking. Blocking occurs when a group of hunters are placed at the end of a draw or dried up creek bed or at the end of a row of cedar trees in a field commonly known as shelter belts.
The blockers are there at the end waiting for the runners that fly up late as the walkers push them through the field. If you are a blocker, ALWAYS GET DOWN ON ONE KNEE AND YELL CONSTANTLY AT THE WALKERS TO VERIFY YOUR POSITION AS THE WALKERS MAKE IT TO THE END OF THE FIELD.
As others have stressed wear plenty of blaze orange, don't forget those safety glasses and make sure you have a good, comfortable pair of boots for the walking.
With hunters whom I have known for years, I have a technique for those birds that lay down as you walk over them and get up behind the group: I pull the shotgun, muzzle up, in close to the front of my body pivoting around and once I am pointing in the direct opposite direction, I make the shot. I would not try this at your level but as you get comfortable, it can be a great way to get birds. The catch is toi make sure that everyone knows and expects this to happen.
Many will tell you pointing the muzzle on the ground is safe. I say when you are with one or more people, keep that puppy up in the air. The is too much of a chance that someone could be shot as the muzzle is raised from the ground to the shooting position.
Check and recheck your safety constantly. Remember that in the excitement of flushing birds, it is easy to forget to re-engage the safety after a volley of shots has been fired. I have done it and I doubt there's anyone on this board who hasn't done the same thing.
Good hunting