For a good foundation on which to build your excellent credit history you ought to have 3 credit cards, an auto loan and a mortgage. Carrying more than 3 credit cards may offer you conveniences but the theory that the more credit cards you carry the better your credit score gets only works up to the first three credit cards and even then it only applies if you use them correctly. We will get to proper usage later, in this section we will deal with how many credit cards and loans you have.
If you don't already have a mortgage or car loan don't run out to obtain them just to establish your credit. If you happen to need a car anyway you might want to get an auto loan, if an important short term goal in your life involves needing a stronger credit report. An example of this would be someone with little established credit who knows they want to buy a house in the next year or two. If you have the money to pay cash for the vehicle or already own a car outright but want to establish credit fast don't feel you have to refinance the existing car or buy a new auto with a large loan. The important concepts center on types of credit and credit habits. That means a small car loan will count to establish that variety of credit and paying on time proves the habit.