Definitely the first thing to do when you are starting the game. There are some players who are out of contract at the start of the game. It's players whose contract has expired and have the right to negotiate a new contract with whichever club they want, or players no team wants.

You should go to search for a player and use the filter "contact expired". This will show you all of theplayers out of contract. Click on a player, see his stats and do either of the following:

• Offer a trial: You can offer the player a trial period of up to 2 weeks so that you can evaluate him better. Select this only if it is a player for whom yu are the only team interested or he will not accept.
• Offer a contract

It is important that you realise most of the players out of contract are just crap you don't need to care about. However there are a few that are out of contract just because their team could not keep them. The most classic exception, is Taribo West. This is a DLC almost any CM manager tries to sign at the beginning of the season.