Start with caned air or air puffer. Do not use any type of paper (napkin, paper towel, etc) no matter how soft it might feel. Ony use cloth, lens cloth, microfiber or equivlent.
I use a lens cleaning solution. Do not use windex, or anything with harsh chemicals, ammonia, etc. Also better to use a damp cloth to start and finsh with something dry. Wipe gently, etc.
Bay Area - CA
~R5 C (184.108.40.206) ~RF Trinity, ~RF 100~400, +Canon Control Ring~6D2 (v1.1.1) Retiring ~EF Trinity, others ~DxO PhotoLab Elite ~Windows10/11 Pro ~EVGA RTX 3080Ti FTW3 Ultra ~ImageClass MF644Cdw ~Pixel6 ~CarePaks Are Worth It