Another tip from mega-platinum engineer/producer Keith Olsen: use the shape of your room to your advantage when tracking. Here’s the idea: when recording a directional source, such as a guitar amplifier, don’t place the amp/speaker so that it is parallel or perpendicular to the room’s walls. Rather, turn the amp at an angle to the walls so that reflections bounce around the room, rather than directly back at the amp. Likewise, angle the amp upward so that the reflections from the ceiling are directed away from the amp.
Think of a flashlight shining into a mirror; rather than have the light reflected straight back into your eyes, angle the flashlight so the light reflections bounce around the room.