The biggest way to protect yourself as a co-signer is to have good communication with the primary borrower. Make sure they can come to you before there is a problem if they are unable to pay. You may need to cover the loan for a month or two while they get things in order. It is much easier to cover for a primary borrower for a few months than have them be too scared to speak with you sending the loan into default. You can always float them a small loan on the side to help them through a rough patch because once a loan goes into default, the damage is already done.