My students usually want to sound more like a Norwegian. As we have many different dialects, speaking like a Norwegian can mean different things in different places. Our capital, Oslo, is located in Østlandet, and the dialects in the surrounding area all belong to østnorsk (øst=east). The variation typically taught to foreigners both in Oslo and elsewhere is known as standard østnorsk, that is, bokmål (our most common written language) spoken with an østnorsk phonology.
This includes the retroflex sounds, written as rs, rn, rt, rd and rl. In short, you pronounce rs as an s/sh-sound while keeping the tongue where the rolled r is usually pronounced! This sounds a lot like English sh. Retroflex means that the tip of the tongue is curled up and back, to where the r is usually articulated. The r and s thus merge and create a retroflex s-sound, which is transcribed ʂ with IPA (the International Phonetic Alphabet). This always happens between words as well, unless you make a break between the words. «Vær så god» (you’re welcome, although literally it means be so good) is thus pronounced «væʂågo». «Han er snill» (he is kind) is pronounced «han æʂnill».
When r and n meet, the same thing happens. Norwegian n is pronounced with the tip of the tongue touching your upper front teeth. When an r and an n meet, the tongue is curled up, and the n is pronounced where you would pronounce the r. In IPA, this sound is represented with the symbol ɳ. The word barn (child, children) is pronounced baɳ. The same thing happens between words: «Har noen kommet?» (Has anyone arrived?) is pronounced «haɳoen kommet»?»
Norwegian t is pronounced with the tip of the tongue touching the upper front teeth, but rt is pronounced with the tongue curled up, and can be written with the IPA ʈ. Bart (moustache) is pronounced baʈ. This happens in word boundaries as well, and «Jeg har to» (I have two) is pronounced «Jeg haʈo»
Similarly to rt, this happens with rd as well. Hvordan (how) is pronounced hvoɖan. Most of the examples are found between words: «Er det?» (Is it?) and «Hva gjør du?» (What are you doing?) are pronounced «æɖe» and «hva gjøɖu?». Some words are pronounced without this retroflex, keeping the r and d distinct. The word verden (world) can be pronounced ver-den or veɖen, and the same is true for sverd (sword).