Lots of advice on sealing a new deck, curious what the group would recommend here.

Our deck was installed ~3/4 months ago, it has not had anything applied.

Currently thinking/questions:

1. we need to clean it (what is best)?
2. do we need anything to condition after cleaning?
3. do we need to sand it before stain (people seem mixed in this one)
4. semi-transparent stain and seal (any recommendations)

Also what are common mistakes to avoid?