you're dealing with just needs to be completely clean and free of debris, so that you're left with a clean, even surface upon which you can start laying down your new flooring. so you need to make sure you remove or repair all nails, staples, or anything else that makes the floor uneven, bumpy or jagged.
for our project, we thankfully found the sub-flooring to be in good shape and it was a simple process for me (and my helpers!) to pull all the remaining nails and staples from the floor (using pliers), and to also remove the narrow wood carpet strip from around the perimeter of the floor (using a 