Hard time starting my car.

i'm not very good with cars.. so i have this question and i hope i can get some good input. My car has trouble starting, it takes a good few seconds of holding in the key for it to fire up, but once it stars the car runs great, has a lot of power and what not. I know the battery is getting old, but everyone i talk to say it is probably not the battery, but injectors or the fuel pump. Anyone have any good idea's? or possible other problems that could be causing this? any info would be great, thanks:)

It can be a number of things; battery, fuel system (injectors, pump...), spark plugs, an electrical or sensor promlem.

dirty fuel filter ??