Suicide pools are a very simple concept that test your ability not only to pick a winner, but to project your winner through the ups and downs of a draw. You'll also have to know what players can easily win an early round match for you, but can be counted on (at least by yourself) to falter as you go through the 14 days of a Slam.
For each day of play, you have to pick 1 - yes, just one - winner each from the men's and women's draw. That is out of all the matches played that day. But, once you pick someone, you cannot choose them again for the rest of the tournament. So you really don't want to pick a Federer Djokovic to win in early matches.
To survive in the suicide pool, you will have to have gone through 14 successive days of picking a winner. Sure it may sound easy (and probably will be) on the first few days of play - but as you get deeper into the draws, you have to start picking based on not only who you think will win, but who is likely to lose down the road. And remember, if you are still alive come semi-final time, you are not only picking who you think would win a semi, but also who would lose the final, since you could not pick the same player again.
Men's and Women's draws are played separately. So if you lose on the men's side but are still alive on the women's, you continue playing the women's draw.
Picks will begin with the release of the Order of Play for Day 1 - you will have until play begins on Day 1 to make your selections. Your selections have to be for a Day 1 match. Subsequently, you can pick your Day 2 winner as soon as the Day 2 order of play is announced, and so on.
Each day, a thread will be started that reads in the header : "Day __ USOSP Pick". This is where you'll post your pick for the corresponding day. There will be separate threads for the men's and women's game. The Day 1 thread will be posted sometime shortly after the order of play for Monday of Week 1 is released, and you will then be able to make your first pick.
And remember, the US Open plays 3 days of 1st round matches on the mens side. And you do need to make a pick each day.