Flushed the coolant and replaced with fresh (see my "Why Can't I Buy Prestone At Walmart" thread).
Every 50,000 miles I do a bunch of stuff and we're approaching that.
The JohnnyO maintenance schedule:
Every 5000 miles change oil and filter, rotate tires.
1x year clean K&N air filter.
Every 30,000 miles change fuel filter, transfer case lube, rear axle lube. Until I hit 150k when both drained out clean so I said heck with it, I'll wait until 50k. Did the transfer case two weeks ago and it still drained out clean after almost 50k.
Every 50,000 miles change coolant, spark plugs, front axle lube (at Valvoline).
Every 100,000 miles change plug wires and serpentine belt.