Exit polls take a sample survey of people post voting with a sample size of 1000 per venue (total size 100k for full elections). They then use the data from that to extrapolate general sentiment and voting trends within a population, per ethnicity, gender, sexual orientation etc.

http://www.pewresearch.org/fact-tank/2016/11/02/just-how-does-the-general-election-exit-poll-work-anyway/

it depends though I prefer short hair

My Enemy - Chvrches
Stone Cold - Demi Lovato
sol. - mausi