I'm going to relocate to Switzerland in a couple of months and being worried about my son going to kindergarten as he doesn't speak either english or deutsch, only russian. Is there some common tipps/techniques how to prepare him for this?

My kids came over 4/6 and 10 without German. They did fine. The acquisition was somewhat hampered for the younger ones as they had friends who would translate for them!

At 3, you don't have worries. Maybe just teach some keywords like danke, toilette etc. But nothing more elaborate.

At 3 years old he won't be going to kindergarten unless you're moving to Ticino; otherwise children have to be 4 years old for kindergarten. You'll need to arrange some sort of daycare.

Krippe (day care) in the local area is ideal - it's not just the language, but making friends and knowing local nursery rhymes and games which will help for kindergarten.

Also customs around how to behave, what food Swiss kids eat etc.

At age 3, he will learn German from immersion. Putting him into daycare will be a good way for him to socialise and make friends, as well as learn German through playing. If he doesn't know enough German by the time he starts Kindergarten, he will be given extra German lessons by the school.

If your child watches cartoons, change the language setting to German so that he can start to get used to the language and pick up some words or phrases.