After taking communion, I see some people go back to their pew and kneel and some sit. What is the proper etiquette? Should I kneel or sit?
Each church, within the guidelines of the Book of Common Prayer, tends to have its own customs for worship. For example, some churches stand for the Prayers of the People while some kneel. Either is acceptable. So is kneeling after returning from communion. The local practice may be to sit or kneel. What I observe at the churches I've been in is a mixture.
It really is a matter of your personal piety - the practices you do to make you feel closer to God. Here's how I approach it. Holy Communion is a sacred encounter with the living God. As I return to the pew and contemplate this, I prefer to kneel because it feels more reverent to me. The person in the pew next to me can be just as contemplative while sitting. Most importantly, either kneeling or sitting, at that moment you should strive to tune everything else out and enter into deep prayer with God. Following that practice can assure us of an even more fruitful experience from communion.