Pre/Post Ride Bike checklist:

Before a ride & after a ride there are always a few things you should check over on your bike.

At a minimum you checklist should include checking:
~ Tire pressure
~ chain tension
~ quick releases (tightened)
~ lube chain
~ proper function of your shifters and brakes.

An expanded checklist might include:
~ Look for wearing and cracks in your cables & brake lines
~ Wheels straight?
~ Inspect the joints and welds of your frame for cracks and chipped paint
~ Tears in your tires (in pattern and sidewalls)
~ Overall tire wear
~ Inspect brake pads
~ Chain length
~ Inspect cassette and chainring teeth for excessive wear.
~ Nuts and bolts tight on: Cranks, pedals, handlebar, stem, headset, seatpost clamp.

Personally, I like to clean my bike after each ride, this usually means using "Honda Polish" (mc polish, similar to furniture polish for bikes) or good old mild soap & water. This really helps you look over your bike well. When drying off, look for paint chips, stress cracks, and cracks in the welds of your frame.