From my experiance, the 3 most important things are:
ALWAYS pay on time. Whatever it is you’re paying (credit card statements, utiliti bill, medical bills, mortgage, celular, rent, you get the idea…), never make a late payment. even a single one can drag your score down.
Keep your utilization low. Below 30% Util is my rule of thumb.
Use credit (wisely). I have 3 CCs, one car loan & a mortgage.
Assuming that you continue to make timely payments, it takes around two years to build good credit. Around 70% of your credit score is determined by data from the previous 2 yrs.
Don’t expect overnight results of magic formulas. Good credit score is for long runners…