This is the most common way that I wear denim shirts. Slap on a pair of colored pants, a white tee, and a denim shirt will fit right in. I use a denim shirt to bring my favorite summery colored pants outfits into fall. You don't have to have colored pants to wear this kind of shirt, though. Many people will say that you can't wear a denim shirt with jeans, but I disagree. I like the denim shirt/jeans combo, but I always make sure that my two denims are drastically different shades.
Wear the denim shirt like you would a flannel or dress shirt. I've been wearing this look a lot recently and really like it. I love to pair this look with jeans and a bold shoe. Since the denim-on-denim blends together, you can really let your shoes be the statement piece.
I have a lot of very loud sweaters and knitwear. A plain denim shirt is a great way to feature these knitwear pieces and avoid the standard white t-shirt. Again, wearing denim and denim is allowed, just make sure they are different shades!
So there are three looks that look polished and aren't hard to put together at all. No more being intimidated by the denim shirt. Some might think they are too expensive, but I found my lighter denim shirt at H&M for $25! Remember, you don't have to drop mad money to look like you have mad money.