What are the requirements to be placed on the practice squad?

Answer 1

Basically, 53 players make a football squad in the NFL. Of those 53, 45 dress to play for a game. The others are considered the 'practice squad'. There are no real requirements to be on the practice squad other than the coaching staff believes that you are the 46th-53rd best player on the team. The practice squad is very important since if someone on the 45 man active roster gets hurt, the first place a team will look to replace the injured player is the practice squad.

The above is incorrect. The practice squad is an additional group of 8 players in addition to the regular roster of 53. For each game, 8 of the 53 players are designated as "inactive" for the game, but that is separate from the practice squad.