Would any of you "indigenous" folk tell me, is this the most common way of saying "at someone's [my friend's] house?" And/or is, "in dem Haus meines Freundes" used as frequently or only in literary publications? Vielen Dank.
I think "bei meinem Freund zu Hause" would be best. "In dem Haus meines Freundes" is very emphasized, as in 'inside the house not on the house' in case you are repeating yourself to someone who didn't catch what you were saying.