till the dust is smaller than 1mm in diameter leave it, as it's not going to do anything with Your pictures, If You really need to clean the lens, here's how I do it:
- check if there are some visible pieces of dust, that can be taken by air blower
- if so, use the air blower
- breathe gently on the lens
- take a clean part of tshirt
- clean the lens with this clean part of tshirt
I've never had any problems with any of my lenses, and I'm using this technique for the last 10 years.
When I'm at home, I sometimes use the IPA cleaner and some cleaning tissues.