Is it a good idea to water the trees heavily for the first week to let the saplings take up water (like soaking for 12 hours), or let the dirt dry out to about 20% or so to let the roots breathe more?
You should soak bare-root trees in water for about 8 hours. Remove any dead roots and plant as soon as you can. If you can't plant, water them and then rewrap in the material they came in until you can plant.
If they have a tap root, you should water them through the spring as well.
The hole should be dug to the depth of the roots, and 2-3 x the root ball diameter, in a square shape. This helps prevent root circling in the hole. Amend the soil if you need with some slow release fertilizers, and bury to the same depth as it was originally buried.