First - proper speakers placement. You should start there.
First reflection points next.
Now... there are 2 schools of "live end - dead end".
1.Live front end - dead back end.
2.Dead front end - live back end.
It is hard for me to recommend which road should you choose, since everybody have a different opinion on this subject. Second I don't want somebody to think that I am an expert on that matter, because I am NOT. What I do have is a lot off experience in set-ups in problematic rooms and my own experimentation and measurements. And NO, I am not a dealer or installer. What I do , I do for my friends and fellow audiophiles. I never charge a stinking penny and I do it for pure satisfaction.
In my own room I implemented treatments according to my rooms particular problems. All room are more or less different from each other and that makes it more difficult to recommend one solution over the other.
My own preferences is semi-dead front end and live- diffused back end with just a little absorbing.
Trick is to not to over treat you listening room. Believe it or not but some reflections are beneficial and you don't want to kill all of them. Ceiling treatment and bass tweaking is another matter maybe for another thread.
Mariusz Stark