Do you like Fall Out Boy? Do you want to be like Pete Wentz? Here's how.
Lay your foundation with a pair of tight-fitting dark jeans or black mod pants. Let the pants taper a little bit so that the bottoms of the pants are fairly fitted to your legs. If you can't find those kind of jeans or don't like colour black you can choose for bright colours such as yellow, orange or red.
Put on a fitted T-shirt that's either black, plain white or ironic in some way (think about out-of-the-way diners or local BBQ houses). Throw a dark colored hoodie over the t-shirt and keep the hood on.
Lock on some old school skate shoes or well worn Chucks and accessorize with head wear such as a beanie or the Castro-style hat that Pete Wentz often wears. Put on some thicker rimmed glasses, even if they're not prescription. Also go for some masculine jewelry like silver linked bracelets or a heavy chain necklace. When it comes to the shoes, try something funky. Wear bright colored skater kind of shoes.
Change the way you dress every once in a while by going unexpectedly preppy with clean white button-down shirts and 1990s style vests. Keep things interesting by wearing loud colors on certain days to contrast with your usually dark and somber dress.
Keep a side strap or bike messenger's bag around at all times so you can sling it over your shoulder to edge towards an on-the-go look.
Opt for long sleeves and long pants in almost all situations. Try to find sleeves that go to the middle of your hand. If the pants are a bit long take a pretty wide roll to get the Pete Wentz style.
For more ideas look for some pictures or watch videos.