After receiving my new/used 250, I went over it with a fine toothed comb and found a few problems that could lead to serious problems down the road. Here's a list of items I check before and after every ride. Feel free to add comments, you can never know everything.
Pre-Ride
1. Release fork tube pressure.
2. Check tire pressure.
3. Check brake & clutch levers.
4. Top off fuel.
5. Turn fuel on and lean bike over to fill carb.
6. Give 2-3 slow primer kicks before starting engine.
7. Let bike warm up for 4-5 min.
8. Double check your fanny pack.
Post-Ride
1. Completely clean bike. I use small toothbrushes to get all around the hubs and engine. While cleaning I look for loose bolts and hardware. I never use a pressure washer! This can rip off your graphics and/or damage any oil seals and bearings!!!
2. Lube lever pivots, rear brake pivot, kicker pivot (if it needs it), and chain.
3. While cleaning the wheels, lightly tap on each spoke with a spoke wrench. You should hear a slight ring. If it sounds dull, tighten the nipple in 1/8 increments. I also check brake pad wear.
4. Check chain tension.
5. Pull plug and replace if needed.
6. Check water level, oil level, brake fluid level. Check suspension for signs of any leaks.
7. Check tire pressure. While the bike is on the stand check for play in the wheel bearings.
8. I wipe on WD to all the bare metal surfaces, this prevents rust and mud stains down the road. Makes it alot easier to clean your bike after the next ride, too. If you ride in muddy conditions, you can spray WD under your fenders, this will help with mud build-up.
8a. Clean your air filter. Apply a small coat of grease around the flange to seal the filter to the airbox. (Thx Cam)
9. Sit back with a vodka tonic and look at my shiny ride.