I'm not especially comfortable speaking in front of crowds, but wouldn't be ashamed to hand out printed cards with the following advice to this year's graduating class. Some of the advice is related to fixing mechanical things, some of the advice is about life in general, and some of it could go either way.
-"Economical" and "cheap" are not the same when it comes to buying tools.
-If a hydraulic leak stops, it's not because the leak magically fixed itself and everything is now "okay." It's because the reservoir ran out of oil.
-In the mind of a customer, one botched repair erases the memories of 25 successful repairs.
-Smoke from electrical wiring or electrical components is never a good thing.
-The wrench you lose or break this morning is the one you'll need this afternoon.
-Never look at your thumb while swinging a hammer.
-"Fixed" and "fixed right" are not always the same thing.
-Promise less than you deliver. Deliver more than you promise.
-Righty-tighty, lefty-loosey.
-If you have to borrow a specific tool more than four times in a year, buy your own.
-When working on large equipment, never work under anyone who chews tobacco.
-Understand the difference between working for a friend and working with a friend.
-There is a difference between a job, a career and a hobby. Understand why you do each and don't mistake one for the other.
-Don't expect to toot the whistle if you were hired to shovel coal.
-You can always re-do repairs because machinery doesn't remember. It doesn't work that way with family members, spouses, friends, bosses and customers.
-If you're the one who toots the whistle, remember that somewhere, somebody is shoveling coal to allow you to do that.
-Never say "never." Unless it's in regard to ethical or moral questions, and then have personal standards about when to say it.