Determine first if your goal with your flock's offspring is predominantly meat or egg production. You'd be looking for different genetic qualities of your rooster for these two different mindsets. For meat, you're looking for girth, a big meaty breast, plump legs etc. For eggs, you need to observe how much space is between his pubic bones, you can find these bones by feeling his abdomen and then with your hand held against the bird, count how many fingers fit between these bones. A rooster that will encourage larger eggs and less problems with reproductive issues in their daughters, will measure about three to four fingers wide (depending on if you have 'man hands' or 'small hands'). The more fingers that fit in this area, the greater potential for large eggs, and easier laying for the hens.
Meat and eggs are not the only factors to consider when deciding which rooster to keep. I cannot stress enough how much the cockerels attitude matters. Do the hens or pullets RESPECT him, do they seem to congregate around him or do they take off running when they see him? If your pullets and hens don't like him, respect him, or trust him, they'll likely reject his advances which could end in nursing your hens for his amorous attempts. If you only have the one rooster, he WILL demand that they mate, and if the hens aren't willing, he will TAKE what he wants. Just saying, be aware of the flock dynamics and who's diggin' who's vibe. Does the rooster candidate respect you, and everyone in your family, including pets? If he's not friendly, that's okay... but if he's not the cuddly sort, he should give you, and everyone in your family a wide berth. This is his way of displaying to you and all of the flock, that YOU are head honcho, and that he respects YOUR authority. This is very important, and moreso if you have pets or children that may come in contact with the cockerel/rooster.
As for culling, rehoming, or processing your other cockerels for the table, this becomes easier over time. There are some excellent youtube videos that go in great detail on how to perform the processing of your poultry for the freezer.