To be successful in Guaranteed Prize Pool (GPP) leagues, it takes a different strategy than head-to-head (H2H), double-up (DUP) or even 3man leagues. In smaller leagues the main goal is to create a team with the most projected fantasy points possible. This team, based on your opinions would have the best chance of finishing above average.
In a GPP, finishing slightly above average is no different from finishing dead last. In both cases you lose your entry-fee and get no prize. So, you need to make the team with the highest likelihood to finish in the top 10%, or maybe even 1%. Maximize your upside, not just your value. When all else is equal (or even close to equal) you should choose the guy with MORE risk when building a team for a GPP. Here is an example...
Judging from the GAMELOG provided in the player's Full Profile (which you all should be using) it seems Stephen Curry could score somewhere between 20 and 50 fantasy points on any given night and he is averaging 35 fpts per game. On the other hand, Blake Griffin seems to hover in that 30 to 43 range with an EV of about 36.5 fpts. For an H2H league you probably take the extra 1.5 fpts in expected value, but if you're trying to win a GPP you might go with Curry for the extra 7 fpts of upside.
Another thing to consider for GPPs is uniqueness. Sometimes it's worth giving up a small amount of value to gain some uniqueness. This can be tough because you don't always know which picks will be popular, but over time if you're paying attention to the percentages next to players on the scoreboards you can start to see trends/tendencies.
Here is an example from a couple weeks ago...
When D.J. Augustin first got hurt, you could assume a lot of people would jump on Kemba Walker. However, he was playing on the road against a top defense, the Chicago Bulls. The tough matchup might not be enough to leave him off your team in a DUP or H2H league, but adding in the assumption that he will be a popular pick tonight, avoiding him might be a good way to gain a leg up on your opponents. To oversimplify, maybe you think Kemba will do better than DeAndre Jordan (who is the same price) more often than not, but maybe you think Jordan will outscore Kemba 40-45% of the time. If you think maybe 60%+ will have Kamba tonight in your GPP, but almost nobody will have Jordan then you are getting very good odds to roll the dice with Jordan.
Projecting fantasy output is still the most important aspect of building any team, but when projections are similar, factoring in potential upside and potential uniqueness can take your GPP game to the next level. Some of the popular picks are too good to pass up and you don't always need to load up your entire team with boom or bust players, but you need to remember you're not looking for a nice little 20% return here… in the words of Ricky Bobby: "If you ain't first, you're last."