We built our house in 1999, with the basement planned for a workshop and railroad. Our snap ties were sealed on the exterior of the concrete with silicone sealer, prior to backfilling. We got the "damp proof" black stuff, too, but we chose to site the house on a knoll with very good drainage. We, too, had professional landscapers destroy our carefully graded backfill, so I had to sink an extra drain out there, which solved a minor ponding problem near the foundation.
The first step in preparing the basement was the radon test. We built on New England shale (with lots of quartz), with the striations facing upward (visualize a sliced loaf of bread), so we found plenty of radon. I am not convinced of the epidemiology of the radon issue, but I decided to err on the side of caution. The remediation was a simple hole in on edge of the floor slab, and a suction pipe with a vacuum pump that works 24-7. The radon tested OK, and as a result, the basement seemed drier.
Which brings me to the main point: our basement is nice and dry There are several vertical shrinkage cracks in the concrete walls, most plugged with caulk by the radon crew, but no water is seen anywhere, even during the worst rains. We have had leaks from upstairs, through the framed walls, but these were repaired when I tracked down the source (kitchen exhaust fan hood inadequately shielded).
I have a dehumidifier that runs all summer, but it never kicks on when the heat is on. It drains into the central AC condensation tank, which has an automatic pump which lifts the water up and out through a 1" plastic pipe which dumps outside in a flower bed. The hydrangeas love it. The dehumidifier is by White-Westinghouse and has worked great for 9 years, so far. The humidity gauge shows no more than 55% humidity, usually 50% in the summer, 25% in the winter.
I prepped the walls in the layout area by drilling blind holes and inserting lead plugs, then screwing 1x2 nailers on 24" centers. I fit 1" pink foam slabs between them for a little insulation. I used horizontal 4x8 sheets of sheet rock horizontally, with nothing on the lower four feet (bare concrete) as my layout is at 50" or above. I wanted to avoid the local taxman ruling that I had a fully finished basement, which has worked so far. The ceiling is 1" blue foam board nailed straight to the studs, with cutouts for a few hot water pipes, sewer pipes, etc. The foam board is very cheap, easy to install, and creates a nice sky effect. Track lighting was installed under the ceiling, tight against it. I used crown molding where the sheet rock meets the ceiling; it fits my idea of how a "room" should look. There is a corner I could have coved but I just squared it in, normal room style, as there will be Brooklyn buildings there some day. The adjoining wall has three double hung windows which let the sun in during the winter (they face south), so the diorama effect of a coved corner would be lost with the windows so close.
I'm sure there a few typos here but I have to go "out", sorry.