A credit score is a summary of how reliably you have repaid borrowing in the past. Lenders use it as one input when deciding whether to offer credit and on what terms.
What usually matters
Paying on time is the biggest factor. How much of your available credit you are using, how long you have held credit, and how often you apply for new credit also play a part.
Habits that help
Set up reminders or automatic payments so nothing is ever late. Keep balances comfortably below your limits. Apply only for credit you need, and check your report regularly for mistakes.
Small, boring habits beat clever tricks every time.
General information only, not personal financial advice.