In my experience its a combination of knowing where to stop and where to not, along with colors that blend well. Personally, i've found this combination to work well. Light green patterned button up shirt from Goodwill, OD Green GI pants, (in fall i switch to real-tree pants, and brownish patterned shirt) and mask paint for the season (i have several "spares").
To the people who've said things like, just have dark colors and such. In my experience, the darker something is, the quicker i see it. I've generally found that things like camo need to be a bit lighter in shade than you think b/c once you get into a woods, everything looks darker than it did by itself because you are under branches and such that are blocking the direct light. This also allows for fewer contrast lines with lighter objects behind you wherever you are hiding/moving.
Also as stated, its knowing when/how to move. I've had alot of moments where i knew for sure i was dead, then they turned and walked away b/c they didn't see me. I spend most of my woods time doing flanks and maneuvers, and most forms of camo help more than they hurt.
To a slight contrast to one thing that some have said, i've found that some rather unconventional color schemes (not exactly natural) can be incredibly useful in a wooded environment (so long as it doesn't have much black).
Masks and Guns are the first things i usually see when looking for someone, if you're not going to attempt to camo those, camo clothes will only be marginally helpful.
My 2 cents.