Asking for your credit limit to be raised can improve your credit score

Keep your credit utilisation – the amount of credit you use compared to your credit limit – low to boost your all-important credit, advises Diana. “You can borrow less, or you can ask for a raise in your credit limit.” A recent study from CreditCards.com found that only 28 per cent of respondents have never asked for an increase in their credit limit. However, a whopping 89 per cent of those who asked for a credit limit increase received one.
Unless they have a high annual fee, don’t close your old credit cards

“The longer your stable credit history, the better it reflects on your credit score,” explains Diana. “The age of accounts is averaged over all of your credit accounts, so closing an older account that is infrequently used actually harms your credit score in two ways: it lowers your credit limit, which raises your credit utilisation; and it lowers your average account age. If you have an old card with a decent credit limit, use it at least annually to keep it open. But don’t forget to pay the bill on time!”
Don’t ever co-sign a loan

“Co-signing a loan isn’t just vouching for someone’s character,” explains Toomey. “Understand that if the borrower doesn’t pay, then you’re responsible for every single missed payment. If they don’t pay, it’s your credit that will be ruined.”