If you are taking a walk around the block with your child, ask her how long she thinks it will take for you to complete that walk - have a stopwatch with you to record exactly how long it takes. If you are sending your child to her room as punishment, tell her how long she has to stay in her room, and set a timer. The same applies to TV time or time on the computer. Let her help to set the timer - it will give her an idea of how long she is on for.
While playing games as well - you can teach your preschooler to tell the time. For instance, you can ask her how long it would take her to run around the garden, or how long it would take her to find a puzzle piece.
Cooking and baking as well will also give your child a good idea of time. You can let her help you set the timer for those cookies and then watch through the oven to see how long it takes them to bake.