I think this is probably a bit "nit-picky", but here are my common sense guidelines concerning pocket squares: 1. Formality of pocket squares can be loosely based on the material and color of square. A white square, in my mind, is always going to look more formal than a paisely or polka dotted one. I feel like a silk square is going to look more formal than a linen square, but I think that might be an individual thing. 2. Certain folds are going to look more conservative than others. The tv fold, or one where just a sliver of square shows, might be construed as more formal by some people. Conversely, a brightly colored paisely, especially when plopped in the pocket in a haphazard way, is going to look a bit more informal and sporty. When I wear my tuxedo I wear either a white linen or white silk (with black edges) square, and I put it in there in the exact same manner I would normally. I like my square with a few points showing, all angled toward my shoulder. Im sure its just in my mind, but I feel like it makes my shoulders look broader when I wear it like this. Ive always found the tv fold a bit stuffy, but if it works for you, go for it. I like mine to look like I put it in there and forgot about it.