I love jeans, I actually wear them every day. I wear jeans so often that the tan leather seats in my car are stained blue from the constant presence of denim on them. Summers are annoyingly hot here in Texas, but August brings about many things, mainly football and the fall. And from NY to Dallas to LA, when cooler weather breezes in, a great look to compliment jeans is wearing a great sweater, blazer or sport coat. Wait a few weeks for the temperature to fall a bit and you will see well dressed men at dinner or up at the bar wearing jeans, a nicely pressed dress shirt and a sport coat with
cufflinks peeking through the bottom of the cuffs.
Like with anything you wear, the sum is greater than the parts so make sure not to get in the mindset that just because you are wearing a dressier coat that you can skimp on the shoes or belt. Another fashion no-no I have come across is the suit jacket without the suit. Often called an orphaned jacket, suit jackets are made to be matched with their pant counterparts. In rare instances, if you are in a pinch, you can sometimes pair a solid color suit jacket with your casual look. But for the most part, the cut and button type of a suit coat are usually all wrong when paired with jeans.
Here is an answer posted from Esquire Fashion Director Nick Sullivan on the difference between a Blazer, Sport Coat and Suit Jacket -
In the U.S., blazer has come to mean anything that has sleeves and lapels and is worn with unmatched pants, but there are key differences between the three items you mention. In Europe and the tonier parts of the States — especially any place where messing about in boats is a big part of summer — a blazer [above, left] usually means a patch — pocket, navy — blue jacket with gold or (occasionally) silver buttons. The
landlubberly sport coat [above, center], meanwhile, originally derived from the tweedy, robust coats worn while assisting in the untimely end of feathered or furry creatures. It had pockets with flaps, often an extra flapped ticket pocket, and was of softer construction than a suit jacket. As a modern fashion item, it should still retain the somewhat rustic, earthy look of its forebear (even when made in cashmere).
Finally, a suit jacket [above, right] will always be made of the finer stuff, i.e., worsted wool, and smooth to the touch. Still, all that said, it's rarely that cut — and — dried.
Read more:
http://www.esquire.com/style/ask-nick/blazer-vs-coat-vs-jacket-0709#ixzz0O4wdP9Oq