I've been doing this less than 2 month, and I've noticed some sites are great and some sites are crap, some sites where crap n now great and where great n now crap
so all you gotta do is stick at it and check each one every day, your gonna need a laptop tho i paid for one, and nearly got all my money back from when i purchased it
also it goes on who u are to and what your profile says about you n which demographics you fit for the survey.
so this was me last month
shopmium £6.50
grabpoints $5
swagbucks £15
crowdology £5
qmee £5
lifepoints £5
attapoll £4.75
citezenme 0.55
this is me this month
snapmyeats £10 amazon gift card
pollpass £5
lifepoints £10
ysense $10
qmee £5
voxpopme £10.80
panelbase £12
isay £10 Amazon gift card
valuedopinions £15 Amazon gift card
intelizoom $10
and at the moment I'm getting loads of panelbase cash surveys at around £1ish
intelizoom, newvista, yougov, populouslive pay out monthly to yearly, depends what surveys you, yougov took me 2 years but at the time i wasn't skint enough to do um regularly,
all you got to do is find what u like best and what works for you