Do not let contracts expire; resign players immiedately. If you do not, in January teams will offer your player(s) pre-contracts and sign them for nothing.
Free players
During January through April, players will have two or three months remaining on their contracts. You can offer them a contract without money. If you have the wages they will accept. Also, watch players who go on loan. Once the loan is up, offer them a contract before their actual team does. For example, Cisse from Liverpool who is on loan to Marseille will be free transfer from Liverpool. Also, Walcott will get loaned out in January. After the loan offer him a contract. Make to have enough wages to get them.