If you are talking a gray dress with brown boots, my thought is to pull it together with a gold necklace. The gold will relate to the brown boots. This is what Angie did in her blog post on wearing sack dresses with slouchy boots. I was taking lots of notes on that one, as I have never paired brown boots with black dresses!!

I just recently purchased a long gold link necklace that has black, cream, and soft green stones in it, to help pull together similar outfits. Something about silver necklaces (my usual) with brown boots just doesn't work. I imagine the same goes for hardware accents on your handbag too.

Also it needn't be gold - bronze would probably work too?

There are many shades of brown or tan and of grey. They can be pinkish, yellowish or greenish. You might experiment with shades. You might also pay attention to texture when doing an all neutral outfit. I like for one piece to have some shine.