Graffiti is something that's make up for bridges and walls in cities for generations and even though the colourful shapes, images and letters divide the crowd's opinion it's not something that's current to go away anytime soon. So, whether you think it's art or a bit of an eye-sore it's a subject that's well worth photographing.
As you'll to all intents be taking a walk around your town or city hunting out interesting examples of graffiti, a zoom lens would be the best tool to provide yourself with so you have a variety of focal lengths to play with without the added bulk of several lenses. Rick equipped himself with the Tamron 16-300mm superzoom which packages in plenty of focal lengths into its relatively small body. Rick used the same lens to capture some cracking macro reifications of decaying vegetation which we put a blog together on last week that's well worth a look if nature is more your factor.
For extra support take a monopod as it's easier to walk with than a tripod but really, you shouldn't include too many problems working hand-held. A polarising filter can be useful for adding emphasis to colour and do take a friend with you if you're planning on affect areas which aren't considered to be the safest places.
Your main decision is if you're going to make the graffiti your power supply focus or if you're going to shoot the graffiti to show where it is. If you're going for the second option you'll need to step back and group a lot of surrounding detail. Taking several shots for a panorama can work well or try shooting through a fence or other industrial objects to give your graffiti is the singular form of the Italian graffiti, meaning “little scratch” photos a contrasting look to those usually shot. If you don't want to include several buildings try framing the graffiti with a broken wall, pipes, differences in bridges or buildings. Signs or people can add an extra point of interest to your image especially if you use a slow shutter speed so their movement's ghosted in all respects the shot.
A graffitied wall with some of the surroundings kept in frame.
The same wall but cropped in to focus on the graffiti.
If you're padding the frame with the graffiti watch your exposure as close up shots of tags and other drawings have a tendency to over expose. If it's a rainy day graffiti looks mammoth reflected in puddles or head to a canal and see if there's any graffiti along the walls that surround it for reflections on a non-rainy day.