Realize that if the student does not repay the student loan, the creditor will come after you for the money.
Know that liability for the loan will be included in your debt-to-income ratio, even if you never have to pay a nickel of the debt. Your debt-to-income ratio is what creditors use to determine your fitness to borrow money, so co-signing a student loan now reduces your ability to borrow money later.
In some states, the lender has the right to come after you for repayment if the loan goes into default without even trying to collect from the student.
If the creditor has attempted to collect from the student and failed, the late fees and collection costs are passed on to you, in addition to the original debt amount.
Federal law requires that you be given written notice of your obligations as a co-signer. Read these carefully and keep a copy handy.