There is a section in the Owner’s Manual for your camera on “Care and Cleaning” of your camera. If you follow them you won’t have to worry about harming your camera.

I have used Pentax and PhotoSilk lens cleaning cloths for years. Any camera shop should have a selection so just choose one and use it. In 37 years I have never used a liquid lens cleaner. For stubborn smudges just breathe on the lens and use the cloth. I also use the lens cloth to clean my glasses.

While you’re buying your lens cloth, buy a Haze/UV filter to protect the front element of your lens. Choose from Heliopan, B+W, Singh-Ray, Hoya or Tiffen. Don’t be tempted to “cheap out” when buying any filter. Its better to clean a filter than the front element of your lens.

You may as well add a circular polarizer filter to your shopping list. A polarizer will darken a blue sky and remove glare/reflections from water, glass, snow, sand and painted metal – but not polished metal. It will also enhance colors. Choose your polarizer filter from the aforementioned brands.

Cleaning lens and sensor is bit of a serious task.

You may want to read some professional suggestions on this … checkout following URLs

Also one word of caution, do not clean lenses and sensor often with liquid. Lenses might loose their coating, which may be degrade the photo quality

Good Luck