I used to do these all the time back in college. Great way to feed a lot of people
My usual recipe is:
Sausage - over the years, I found that this is what people immediately devour. I usually get the Keilbasa type. Get whats on sale. There is usually some kind of buy 1 get 1 free deal on this type of sausage. I'd go for 4 of those U looking links for 10 people.
Red potatoes or any other starchy variety. Do not use russet! (1 of those plastic sacks will probably do for 10 people. I think its 5lbs)
Shrimp - If you go heavy on other ingredients, I found you can skimp on the shrimp if its expensive. 1/4 lb per person is a good starting point though.
Corn - I usually buy the small ears of frozen corn. If its in season, there is nothing wrong with fresh though. Cut the whole ears in half if you buy fresh. I usually do 1 peice of corn per person, and a few extras. Not everyone will eat 2.
Fill the fryer about half full with water. Season with Old Bay. Go pretty heavy handed. Once the water is boiling, put in the Potatoes. Reduce boil. When potatoes are about half cooked (usually around 10 min), add the sausage. Cook for ~5 min, then add the corn. Cook for another 2-3 min. Turn off the flame, then add the shrimp. Let it sit for a minute or two to cook the shrimp.
Another option is, to dump in everything once the potatoes are fully cooked. I kind of stage it so the water doesn't loose a lot of heat at once. The end result is that you want the potatoes fully cooked, but not so done that they start falling apart and get all over everything else in the boil.
At this point, you need to remove the water. I usually get a helper to hold the lid on while I dump the pot. If you have some sort of strainer, that works too.
The easiest way to serve is wrap a table in plastic bags, then dump the boil onto the table. Have some mustard for the sausage, some cocktail sauce, butter and a lot of napkins!