Timothy Strobel didn't realize the risk he'd encounter when he tried to mow his lawn after days of heavy rain. His mower got stuck in the mud near an air conditioning unit.    Timothy Strobel, "I leaned forward to pull the lawn mower out of the grass, and I slammed my forehead and my neck into the actual unit itself."    Dr. Andrew Peretz, who treated Timothy for a severe concussion and a spinal cord injury, says accidents involving lawn mowers are almost always serious.   Dr.Andrew Peretz, "We've seen the traumatic injuries, the hand getting stuck in the blades, the foot getting stuck in the blades. Unfortunately those are life-changing events."      Consumer Reports' mowing expert Peter Sawchuk says blades on today's mowers can exceed 200 miles per hour. And any debris encountered can become a projectile.  To demonstrate, Consumer Reports mowed over golf balls. Sharp pieces flew more than 100 feet. That's why it's so important to keep kids and pets well away from where you're mowing.  A survey by Consumer Reports National Research Center reveals all too many people have bad mowing habits.   "More than half of those surveyed wore shorts while mowing, and fourteen percent wore flip-flops."  Another really bad habit -drinking beer or other alcohol. Eight percent admitted to doing just that! Consumer Reports also cautions against disabling safety features, such as a handle like this that automatically shuts off the mower when you let go of it.  Another precaution - to avoid slips and falls, don't mow wet grass - something Timothy learned the hard way.