Are there any quick, reliable methods for setting someone's clothes on fire? Please see details.

Alcohol does funny things ;)

Who here is incredibly relieved to hear that you aren’t planning on using this method to deal with a painful breakup? I know I am.

How about some cooking sherry and a pastry torch?

Fill your mouth with booze from a flask. Blow booze from mouth past a lighter in your hand.

Lighting and throwing a match.
Rip off the head of a match and squeeze it between the matchbook cover and the flint. Then snap your fingers and the match head will fly.

In the movie Cape Fear, a girl throws alcohol or lighter fluid (can’t remember) on her kidnapper just as he is lighting up a cigarette.

@Mariah Wow, that’s pretty badass. :D

Tequila, fire and a shot of lime for drama

Build up a day’s worth of gas, turn your back on the kidnapper, let it all out and light it.

A magnifying glass.

http://www.pennlive.com/midstate/index.ssf/2010/08/cumberland_county_disabled_wom.html

Take a can of flammable liquid and hold a lighter in front of it. Instant blowtorch. Because the propellant in most cans of air freshener are flammable, almost any can will do ya.

I agree with @cazzie . My sons, the pyros, showed me the old hairspray and lighter trick a few times.