I highly recommend that you get into the habit of doing a quick safety check of your bike, before each ride.  It only takes a couple of minutes and it could save you from a mechanical issue or something much worse.  Here is how I do a safety check of my bike.

• I start at the front wheel hub and quickly check that the quick release lever on my skewer is secure.  This is followed by a quick check of the wheel spokes, to make sure none are loose.
• Next is the front tire.  Slowly inspect the whole tire looking for excessive wear or damage.  I’m also looking to see if there are any foreign objects embedded in the tread.
• Move onto the front brake. Check that the pads are not too worn and check the brake is operating correctly.
• After this, I quickly check all cables to make sure they are not damaged or frayed.
• I then move down to the bottom bracket area and do a quick inspection of the front derailleur.  I also take a quick look over the chain and chainrings, then spin the crank and listen for anything unusual.
• It is then onto the seat to make sure both it and the seat post are secure. 
• This is followed by inspection of the back brake and rear derailleur.
• Finally I inspect the rear tire, rear wheel spokes and the rear quick release lever.

This might sound trivial, but in the past I have discovered loose quick release levers, damaged tires and worn brake pads.  

In addition to this quick safety check ahead of each ride, every time I clean my bike, I do a more thorough inspection for damage. I  also check that all the bolts are correctly torqued.  I do this roughly every other week.

Bike safety is very important.  You can’t always control the road surface or other users of the road, but you do have control of how safe your own bike is.  Get into a habit of checking it, before every ride.