Being the first-time owner of a decent DSLR, you may have or intend to only use the provided kit lens for all your shoot as long as its possible. And perhaps, you have heard or are led to believe that interchanging lens frequently will only adulterate the cleanliness of the sensor.
But you may (like me) also encounter more of the dreaded "F--" error on the control panel when you switch the Nikon D90 on. Reason? The CPU contact points are just too new and are not properly seated in contact with your CPU contact points on your kit lens.
Solution - Do manually unlock and lock your kit lens (without the need to remove the lens from the body entirely) into position occasionally before each shoot. You only need to do this for a brief month or so as the sensor points gets seasoned and responsive with a lens itself.
Cleaning the sensor points with a lint-free cloth on both the body and lens is also advisable.