I've written multiple times about my own bankruptcy and having to deal with the aftermath of a ruined credit score. I have also had to learn ways to bring my credit score back up to a good level.
The classic way and most common suggestion is to make sure that you make all your payments on time and keep your debt ratio around 30-50% (or less) of the credit that is available to you. These two ideas will never fail in helping you achieve and keep a good credit score, but there are a few other ways as well.
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This final option is one I purposely placed last as I don't think it is a great idea, but is an option if trust is very strong
When you become an authorized user on someone else's credit card, the credit/debt ratio is reported on your credit report as well as the master account holder. As long as they keep the account active and in good standing it will look good for you as well. The best way to be an authorized user is to have them call the company and add you, then when you get the card, give it back to the master card holder as you don't have to use it to reap the benefits.
You will need to display at least one year of positive credit habits to be taken seriously when you pick up a car payment and especially for a mortgage.