I am very careful to only sign up to survey sites that I know pay out as there are many out there that either just take far too long to pay because you need to reach a large minimum payout amount or just do not pay at all. I thought it may be useful to point out which ones I use and how I find them.
My favourite survey site is You Gov. They only pay out when you reach £50 which does take a long time considering they sound out surveys once or twice a week that pay around 50p each. However, what I love about this site is that the surveys are used by newspapers and websites and so my opinion counts towards statistics that are used publicly They are also often about government policies and I like to feel that by giving my views there is a chance that I may be having an influence. I have been paid several times by this site, once quite recently so I trust them and they send surveys regularly. You do not have to complete all of the surveys sent and they do not seem to penalise you for this, so if you are busy, then this is not a problem.
I am also a big fan of Brand Institute. They are an American company and pay in dollars to Paypal for each survey that you qualify for and complete. These tend to be about medical items, but can be more general as well. They are quite strictly screened and often, if you do not have a medical condition or know someone with one, you will not qualify. however, they do pay really well and I have always been paid when I have qualified for a survey and completed it, although it can take three months to get the payment.
I am trying a new survey site at the moment called Hiving Panel. You do not earn very much per survey, but even if it is full or you do not qualify you will get a small credit to your account. You can get payouts to Paypal and the minimum is just £4. I am very close to my first payout, but have not yet claimed it. I felt I would give the site a go as the payout was so small, but I often do not qualify for the surveys.
The last survey site I want to mention is Pureprofile. I have recently started using them again after years of not doing so. This is not because I did not like them, in fact I had a payout in 2010 from them of £25, which is the minimum amount. However, I have been ignoring their emails, thinking they were for some other company that I had been earning money through! I have therefore decided to start using them again and will hopefully be able to earn enough money to get another £25 payout.
There are many other survey sites out there, but I have wasted time on sites where I have never earned enough to get paid out from or just found they did not pay enough or never paid. Therefore, I am always careful to only use ones that I trust.