How often are credit scores adjusted?

Does anyone know how often credit scores are adjusted?

For example if I close a credit card or pay off a debt–how long will it take to appear on my credit report and reflect in my credit score?

Other than paying off debts and closing inactive credit cards–what can be done to improve an existing credit report and score?

It can take a couple months to see changes in your credit report. However, closing inactive credit card accounts will result in a negative effect on your FICO score if by closing them you reduce your credit to debt ratio