As mentioned, definitely some type of background if you can find one. Break up your silhouette.
Also, something I've started doing in recent years is I hunt standing up as opposed to sitting down. I find a big tree that I can stand in front of (or behind) and clear all the leaves and debris away from the base. This allows me if need be to be able to move around the tree quietly, whether to keep a deer in sight or to keep the tree between me and the deer. My other reason for doing this is when you stand in the woods and look out through it, what catches your eye more? A tree or a stump? The stump, because it looks more out of place. When you are sitting, you look more like a stump, and when standing, with the correct back drop, you look more like a tree trunk. I switched to this a few years back and the number of deer that have picked me off has declined significantly. I've had deer walk 5 yards past me without ever even looking. Had I been sitting, I definitely would have been busted.