After some searching, researching, and all sorts of designs of my own (even different scales), I came up with this track plan, which is based on a plan from Kalmbach's 101 Track Plans (see Planning for more details).  Minimum radius is 9 3/4", and maximum grade of 3%.

I used Peco code 55 electrofrog turnouts and flex track, except for a couple of spurs, where I used Micro-Engineering code 40 flextrack.  The 15 degree diamond crossing in the upper left hand corner wasn't available from Peco, so I ended up using Atlas code 80 for that particular piece.

While I was in the process of doing the full size mockup, I realized that I had room for some staging tracks below the passing siding.  I didn't show it in the main plan, because it gets a bit confusing, but you see where they are located in relation to the rest of the layout in the drawing below.  To squeeze everything in there, I had to use a Peco code 80 small radius turnout (as in, appox. 9" radius) in the bottom right-hand corner, 9 3/4" radius curves, and a curved turnout.

Depending on whether the layout is located against a wall, or in the middle of the room, I can add extensions for staging.  Below, you see a staging extension (at the top) that I can build to expand the capacity of the staging from two to four trains, and also allow for longer through trains that might be used in some operating schemes.

I also built the interchange track to the edge so that it could be connected to something like a separate staging track (as illustrated to the left of the staging plan), or a timesaver.