Identify potential hazards in your home and begin to fix them. Focus first on things that are heavy enough to topple in an earthquake and cause damage to you or others, things like: book cases, dressers, water heaters, large televisions, appliances, etc.
It is a good idea to secure these types of items even if you DON'T live in earthquake country - they would be potential hazards in tornadoes or hurricanes, and are definitely potential threats to young children (there are so many deaths each year from children climbing on dressers/bookcases and toppling them over or pulling over televisions onto themselves).
Here is the Secure It Now focus sheet from the Emergency Survival Program. It contains information and instructions to help you secure potential hazards in your home.