Focus on ensuring the 5 factors that make up the credit score in the best possible position at all times.
Pay all payments on time
Keep the amount of money that you use on credit cards under 30% of the available balance
Don't apply for too much credit all at the same timed, and only apply when you have to
Don't close accounts unless you are being strategic, to keep your length of credit history intact
Diverse the types of credit you have: revolving, secured, installment, as necessary