I'm not entirely sure what I do different, or what answers I've given, but I get at least 2 surveys per day. Some are worth more than others, but I've had enough to get the GS card for the past six quarters. I actually have a balance right now of ~$95, so I could do nothing and still almost have enough for the next two quarters.
I will say that since I oversee the benefits at my company, I tend to see a lot of insurance/employer surveys that tend to pay out pretty well. Usually in the $7 range for ~20 minutes of time. I probably get 3-4 of those invites per week, and usually qualify for 2-3 of them.
Otherwise, I get a lot of consumer ones, and I tend to find the beverage ones pay the best. I also, for the first time, was invited to do a survey in which they sent me a physical product to try for a week (bath soap). That one paid pretty well and I got a free bottle of soap.