We do two 25-minute periods of zazen, or seated meditation, with a short walking meditation (kinhin) in-between. Beginners will receive instructions in correct posture and body usage, belly breathing (fukushiki kokyu) and unified breath counting (sussokukan).
The video below is an excellent reference featuring Meido Moore Roshi giving detailed instructions for zazen.
Here are a couple of useful videos with advices and stretches for working towards a seated lotus posture: