This is a great denim shirt because its simple and a great shade of blue. Unfortunately you cant see his trousers underneath very well but this shirt would look great with black jeans.
Double Denim. Be careful ! This can easily turn into tacky hill billy trash. If you do it right however it can be a hot casual look. This guy does it well! You need to make sure that the two shades of denim you are wearing are neither too contrasting, like a very pale denim and very dark jeans OR they or not too similar. The almost matching denim suit attire can look repulsive.
Feeling colorful? Take some advice from Kanye and wear your denim shirt with colored trousers. This green looks hot, you could go for other colors as well, just don't try and go with a blue though as that could look a little 80's.
Also if you like this idea but feel its a little bit baller ish for you then keep the white shirt underneath but just do up the first 4 buttons.
Denim and Khaki. Nice khaki trousers look great with a denim shirt but PLEASE do not wear them with Cargo pants. When I say Khakis I mean the color of the trousers in this picture. A nice Khaki colored soft cotton trousers. NO cargo pockets!
This shirt here is a nice pick and very very reasonably priced at asos.com . Internet shopping is a great way to stay stylish for those guys who hate going out and shopping but please be very careful and pay attention that you get the right size. Getting the correct fit in clothes makes a huge difference in looking good.