Start your child out with just the second hand. Tell them that each time it goes around is one minute. Then have them time different things that might be a minute or less...making the bed, picking up shoes...stirring chocolate milk, whatever...
After a week or so, show them that the minute hand moves one space every time the second hand goes around...let them watch that for a week or more to really get to *know* it!
Next, have them count the minutes on the clock and show them that everytime the minute hand goes all the way around, the hour hand moves one number.
Give that a week or so to sink in. Then point out that every time the hour hand moves to another number, the minute hand is on the twelve...when the minute hand is on the 12 it is called o'clock (of the clock) and we read the number that the hour hand is pointing to...4 o'clock!
At this point, their understanding will allow things to run a little faster...then they can learn the half hour and the quarter hour...and then learn to recognise the actual minutes...let them time things like their favorite television program, or the time it takes a load of laundry to wash, or how long it takes to make a trip to the post office or grocery store from your home...whatever... 
Although this method spans several weeks or even months, your child will *really* know how to tell time...will never forget it, and will know how to teach it too! 