What about translating literally some Norwegian expressions? I've heard someone says "it wasn't only-only" before now, with a thick accent of course. "only-only" is not a recognisable English phrase. It could only be a literal translation of "bare bare" (for those that don't know Norwegian, this is an idiomatic way to say "it wasn't easy", or "it wasn't a jolly " or some such).
Along the same lines, could be "I'm speaking from the liver" instead of speaking from the heart.
Also if ever there's a Norwegian word that sounds similar enough and means a similar thing, you could just substitute it. Like "bittelitt" for "little bit".
In English we've got words like "policeman" or "flowerpot", two words run into one, with no space in between, which are quite common in English. But these are extremely common in Norwegian; they are a staple part of Norwegian word formation. So if you look at the front page for Skolelinux, you'll see words like "softwareproject" or "schoolnetwork", another hallmark of English that's been written by a Norwegian.