You often can't improve your SCHUFA score overnight. But with a few simple steps, you can really help your credit rating:
Always pay your bills on time.
Cancel any unused current accounts and credit cards.
Check every entry in your credit report for accuracy.
Always pay instalments of any kind on time.
Keep a balance between income and expenditure.
Always keep an eye on your SCHUFA score. Especially, if you plan to take out a loan in Germany at some point in your life.