My daughters yard is a constant slope downwards all the way through except at the top where the deck is then it slopes downward. She wants to put in an above ground pool. How do we level the yard to accomadate a pool?
Sounds like you'll need to terrace the yard to do as planned. Whether you'll need to do retaining walls to hold the terraces back will depend on the amount of slope and the width of the terrace.
For a pool on a slope, you will need plans with precise description on how you are going to support the weight of the pool.
I once built a pool on a slope, the plan check department rejected my plans because they included only 10 caissons and the plan checker wanted 23 caissons. A caisson in the case was a concrete pillar 32 feet deep x 2' wide with 1" re-bars (resembles Freeway overpass columns). We settled for 14 caissons (in 1989 they cost $2,000 each).
You can save some build-up by digging down on the upper end, but that too may need a retaining wall and you'll need to have good drainage there. I'd first seek advice from the local building codes inspector. They can give you an overview of the requirements but can't offer specific plans or recommend anyone specifically for the ended work. What that will do is guide you to the next step and give you a feel for how to make the best choices. Plus it usually makes for a friendlier inspection if that's required in your area. They don't generally like re-inspections either ;)