You can expect to clean it fairly regularly if mine is anything to go by, first step is giving a good go with a rocket blower.
If that doesn't do the trick there are numerous cleaning methods and devices, all with their supporters and detractors
Personally I use a Sensorklear Pen, seems to work ok and shifts most of the stubborn stuff that eludes the rocket blower. There are other gizmos such as sticky pads and brushes that create a static field, not used them so cannot comment on their effectiveness
For smears, grease, pollen etc you will need a wet clean which requires swabs and sensor cleaning fluid, loads of tutorials on the web for that. Some people won't try it, but take it easy and you won't damage anything, sensor (or strictly speaking low pass filter) are fairly hardy things really.
Just make sure you have a well charged battery when you raise the mirror via the sensor cleaning option in the menu otherwise it could come back down during cleaning and cause some expensive damage.
Cheers
Rich