hmm- that's several big questions.

one is -why is it wet? or 'where does the water come from?'

the answer can range from a leaking septic system to a high water table, to a clay layer that's creating a small 'wetlands' in your back yard...and those are just the answers off the top of my head.

do you have a basement? if so, is it damp as well?

is this a new problem? are you new to the house? area?

honestly, if it's not something human caused (leaking water pipes, septic issues, runoff from your neighbor's sprinklers) the 'best' solution very often is to create a bog/wetland or even a pond at the furthest corner of the wet area, and channel the water there, where it can be water, and not get in your way.

And maybe poor roof drainage system..,..or even just an abnormal amount of rain in the area.
Number one problem....where is the water coming from...
Number 2 question....what can you do so it doesn't cause a problem.
Linda C

number three is to find out if your locale's legal requirements will affect you. One poster (from Mass.) has had quite a bit to say on the subject, and indicated a considerable control by the local authorities over possible re-direction of water and changing of wet areas (apparently they were mostly against it).