Tips to Improve Your Credit Score
Try to pay your balance on the credit card before the statement closes or make a partial payment before the statement closing day, like that the credit card company will not report High Balances on your behalf.
Be mindful about credit card applications. Try to plan ahead and decide which cards you will need for your future travel and when you will need to apply for the card in order to get and utilize the bonus. Also try to count in the surprise applications when some credit cards come up with great offers.
Spread your expenses throughout more cards, rather than just using only one so that you will keep your credit utilization low.
If anytime you get denied for credit card applications, try to call the reconsideration line (google: reconsideration line for your certain bank you have applied with), and if you have any existing accounts with them tell them you would be willing to lower those credit limits if that is keeping them from extending more credit to you.