First off, stencil anything. If you wait for the perfect idea you will be waiting for ever. Cleverness is never as entertaining as blatant stupidity, failure and public humiliation.
Obtain a fucking sharp knife. Blunt knives result in fluffy pictures and make the whole process long and boring. Snap off blades of British steel are best.
Draw your artwork on paper, glue onto some card then cut straight through the both. Acetate is apparently quite good but any sort of free cardboard is okay. Stiff 1mm to 1.5mm board is ideal.
Get a small roll of gaffa tape, pre-tear small strips and stick them on your shirt inside your coat.
Find a suitable piece of card to act as a folder. For instance when using red paint cut the stencil into the bottom of a pizza box so when you get paint all over your fingers its not so suspicious.
Leave the house before you find something worth staying in for.
Spray the paint sparingly onto the stencil from a distance of 8 inches.
If you’re in a place with lots of security cameras wear a hood, move around the city quickly and act like a sad old drunk if you attract attention.
Be aware that going on a major mission totally drunk out of your head will result in some truly spectacular artwork and at least one night in the cells.
When explaining yourself to the Police its worth being as reasonable as possible. Graffiti writers are not real villains. I am always reminded of this by real villains who consider the idea of breaking in someplace, not stealing anything and then leaving behind a painting of your name in four foot high letters the most retarded thing they ever heard of.
Remember crime against property is not real crime. People look at an oil painting and admire the use of brushstrokes to convey meaning. People look at a graffiti painting and admire the use of a drainpipe to gain access.
The time of getting fame for your name on its own is over. Artwork that is only about wanting to be famous will never make you famous. Any fame is a bi-product of making something that means something. You don’t go to a restaurant and order a meal because you want to have a shit.