The first thing you want to know is whether the site is legitimate and whether they have a good reputation. There are a number of ways to spot the scams. You want to know how much they pay per hour or per surveys and if there are any extra costs involved. You want to know where they are based, because you may not be eligible for international sites. Find out how they pay in terms of their method and whether they pay daily, weekly or monthly. Find out if they will keep your information private to avoid spam.
These are just a few of the questions you should always have at the back of your mind when it comes to paid surveys.