The secret is in the accessories. But because men tend to come off most suave when it looks like they tried the least, accessorizing—which implies thought—is one of the most difficult fashion practices for us to master. So where to start?
With leather, we say! It's an excellent sidekick to denim because like it, leather often looks better and more unique as it ages. For casual looks, stick to leather with handsome natural finishing, or some that looks slightly distressed, and anything from a plain strap-bracelet to weekender bags, messenger bags, belts, or boots will look perfectly natural with your jeans. Going dressier? Try clean black leather, especially a bag that combines the leather with another fabric like suede. Don't be afraid to play around with grey or even with a pop of color if that's within your comfort zone. As long as you're willing to commit, and your best friends don't stop you, try it out.
Hats are another fairly innocuous item to pair with your jeans. It can't hurt to play with trendy looks (the Amish style hat this season…fedoras, pork pies, and beanies from the recent past) but you'd do well to just go with what looks best on your head and matches your personality. If you can find one, throw on some jeans and a T-shirt and make a trip to a millinery to get some hands on expert advice and a custom-made hat.
Not every man will feel comfortable with a scarf around his neck, but they can be a smart way to punch up a simple pair of jeans and T-shirt for those who do. Not only will a scarf add a dimension of layering, it can give a pop of color and an air of sophistication. Stick to neutral colors, patterns that don't look too fussy and please make sure you're wearing weather appropriate material.
Sunglasses never killed anyone, nor did a wristwatch. And since both serve a function, you can almost always safely accessorize that way. Just keep in mind that you want to look natural, and the surest way to look forced is to overdo it. Some people say no more than two accessories at a time, but grace isn't something you can really quantify. If you're unsure about a piece, take it off. And if you think you may have too much on, you probably do.