The pronunciation of "einen" in normal everyday speech.
I have noticed that "einen" is often pronounced exactly the same way as "ein". When I listen to people then I can hear "Ich nehme ein Kaffee", not "Ich nehme einEN Kaffee".
Which pronunciation would native Germans suggest for learners? Would you recommend to say clearly "einEN" or would you rather recommend to say "ein"?
Germans are generally bad in pronouncing the last syllable of words. They tend to cut it off.
In this case you do not hear "einen" or "ein" but "ein'n".
I do not recomment adjusting by just saying "ein". I recommend to still say "einen" but stress the "ei" and make the "e" very short. I'm trying to find an example in the englsih language that would contain a similar sound. As soon as I have one, I will tell. :)
As knuselwupp alluded to, I think that ein'n is pronounced a bit longer than ein and may even have two syllables (ei-n).
I'd recommend learning unreduced speech first -- natural reductions will come over time as you are exposed to fluent German.
Similarly, I'd recommend saying ha-ben rather than ha-m, sing-en instead of si-ng, etc.