one of the summer's trends in the world of men's fashion is the nerckerchief. I've always been a big supporter of the back pocket square/bandana as it's a timeless, functional, and simple option. But the neckerchief requires a bit more caution and care to execute.
While still timeless and classic, rocking a neckerchief is not as simple as throwing a bandana in your back pocket. What you don't want to do is look like a lame cowboy (unless you're lame and a cowboy), or a wannabe fake billionaire who sports ascots (unless you're a wannabe or a fake, or a billionaire).
Bandana selection is crucial in avoiding embarrassment--go simple and classic in color and pattern. Neckerchief knot selection also plays a big part in this since you most likely don't want to look like a 12 year-old boy scout (unless you're 12 or a boy scout).
When in doubt, just don't even try it. The neckerchief is definitely an accessory for someone confident they can pull it off. But when it's done well, it's killer (see pretty much any picture taken for the brooklyn circus guys over the past year).