Don't Co-Sign on Debt
Co-signing for family or friends on their credit cards, car loans, residential leases and cellphone plans can be a quick way to ruin strong credit scores.
This can impact you negatively in two ways. First, that debt obligation can immediately show up on your credit report, and the higher debt load can impact your credit score. Second, if your friend or family member doesn't make their payments, those missed payments will show up on your credit report. If the account eventually goes to collections, that too will show up on your credit report.