I'll preface by saying I know very little about credit.
Like ernie99 said, you have a credit score if you have any type of loan, which is credit. Things you might not think affect your credit but do is age, how long you have been living at one residence, and your other utility bills/rent.
If you had no loans or nothing, you have no credit score to most agencies due to insufficient history. That is considered very low though, someone (bank manager) told me once (whether its exactly true or not) that no credit history was like having a 350-400 in the FICO system (300-850).
I tell you this because I had a very hard time establishing credit. Back when I was 21yo and trying to get a credit card, apartment lease in my name, $50k earnings in W2, no late bill payments (rent, utility), I was rejected left and right even for a cheapo department store cards like Sears and Macy's. The report always came back the same "Insufficient credit history". It took a cosigned loan (which I didn't need) to establish my credit.
As much as I despise our (US) economy's heavy dependence on credit, I suggest you establish and build a good credit history ASAP.