I think when it comes to disciplining a child, some main points would be to be consistent, patient, and also not having double standards. If you are enforcing a rule, it is best to lead by example and keep to the same rule yourself.
Here is a useful article on how to discipline your child (at various ages):
http://sg.theasianparent.com/smart-ways-to-discipline-your-child-at-every-age/
For toddlers, the article suggested:
- explaining to your child about what he/she has done wrong
- giving time out
- removing your child from the situation
- withholding privileges (favourite toy, television time etc) for his/her misbehavior
Hope this helps!