Some good points above:
For the 210:
For boggy or rough strips, takeoff with full flaps, get airborne (about 50KIAS) the hold it in ground effect and retract the flaps slowly stage by stage. The force required to keep the nose down is remarkable.
DO NOT pull the aircraft out of a bog by the front nosewheel. It rips them out.
Clear an area of stones directly underneath your prop to prevent stone damage on startup. Do all your prop cycle and mag checks whilst moving (backtracking) on dirt runways.
Carry a small toolkit in addition to your survival gear. Include tiewire and duct tape.
Mark every forced landing area that you see on a chart, and take the time to plug it into the GPS. Make up your own code as to how good they are for a forced landing. Prefix 1 might mean excellent - in and out no worries, to prefix 3 will get in with damage. You never know when you will need them, especially if you are VMC on top or worse... Make sure you can use the GPS GOTO NEAREST function quickly.
Practice popping the window on the 210 with your elbow as you lower the nosewheel to the ground.
Do some P charts, and factor them for your operations. from memory, P charts are predicated on full power before brakes release. But doing that will see your prop last about 100 hours.
Treat your engine well, avoid shock cooling.
Know your stall speeds at different weights in turns of various angles.
Get into a mental habit of using the gear as a speedbrake. Means that you won't forget it as you will be way too fast to get the flaps out...
Practice low level circuits, 500, 300, 200, 100 feet. you never know when you might be forced to do them.
Curse the person who removed the ram air wing root vents on the 210 series.
Know where the hydraulic reservoir is (a surprising number of pilots don't) AND CHECK IT.
The 210 is a wonderful machine that deserves respect. IMHO is is harder to fly well (ie ball in the centre, nail set speeds etc) than most light twins. Enjoy!
CS