Another tip that I am currently using works for rectangular rooms. Take the distance from the front of the speakers to the front wall and multiply by 1.6 to get the distance that the speakers should be from the side walls. If your speakers are one meter from the front of the speaker to the front wall, put the speakers 1.6 meters from the side walls. I understand that this may not be possible due to having to place the speakers on a long wall instead of a short wall or because of furniture placement, etc. Try it if you can.