Some people describe graffiti as an art form, but it's also associated with gang culture and bad behaviour.
Graffiti can be great fun, but it is illegal if you do it on something that doesn't belong to you.
Here are some graffiti dos and don'ts.
Don't - graffiti anywhere unless you have permission. The laws are very strict and anyone caught doing graffiti can be arrested and prosecuted.
Don't - buy spray paint as it is illegal for anyone under 16 to do so.
Do - speak to your local council to see if they have walls that people are allowed to graffiti on.
Do - speak to local graffiti clubs to find out where they have permission to do graffiti.
Do - read books on graffiti to get some ideas for designs.
Do - practise on a small scale first before trying it out on a big wall.