Practices in Orthodox services can differ. For example, in some Romanian parishes everyone has knelt while the Gospel was being read, but I have never seen this elsewhere. And as the other poster mentions, full prostrations are done (and widely across the Orthodox world) in certain contexts.

Some churches in Greece and Albania have pews -- the concept was brought back from the North American diaspora where Orthodox parishes were set up in former Protestant or Catholic church buildings -- so you can do all the standing, sitting, and kneeling you might be accustomed too.