Probably the easiest of all, pay your bills on time.  If your credit report shows that you have been late on any of your payments, your overall credit score will go lower.

Its obvieous of course but it is not always the easiest.  If you do not have the funds to pay off your debts, due what you can to at least get it down.

Every time you apply for a new credit card your credit report shows the inquiry which gives you a negative point.  Basically it says that you maybe getting a new credit card.

The longer you have had an account with a company the better.  If you like to switch to a new credit card company every couple of years, stop and just stick with one.

The common issue with all of these steps is that they all will take time.  Patience, patience, patience.