I'm in the middle of doing this myself. Here's a couple of things I do.
As I pick up the eggs, I check for cracks. Cracked eggs get put aside for eating. Identify the fatter end of the egg and write the date on it. I'm collecting from four pens, so my eggs get a couple of identifying initials: J for June, H for Miss Hamilton, and S for Miss Spot.
There is a tile floor in the breakfast room. I place the eggs in a carton on the floor. Pointy end goes down, writing goes up (see the method to the maddness? lol). The cartons are sitting on the floor. I have a board (1"x3"X12") that goes under either the left or right side of the carton. When I add eggs, the board switches sides. Before I go to bed, I try to remember to switch the board again.
Now we can observe and see if day old eggs hatch better than twelve day old eggs. Will Miss Hamilton have a better hatch than Miss Spot? I'm going to show them how to watch the air cell increase in size after marking it with a pencil (around the previous writing, lol). I put all my hatching notes in folders last night so I can show the students how to log conditions of the eggs and the actions I take.
I have eggs in my incubator right now at Day 4. Three random eggs showed a teeny embyro!!!
Btw, if you scan the hatching eggs auctions here, people usually say their eggs will be less than a week old when sent out. On the forums here most folks agree up to a week old are very good at hatching. Up to two weeks old hatch pretty well. Older than two weeks the fertility or viability of the eggs start to drop off significantly.
Hope this helps!