Make sure there aren't any small objects such as coins or buttons on the floor that small children could choke on.  

Keep chemicals out of reach of children.  Children don't know that they are dangerous and they might drink them.

Keep medicines in a locked cabinet or out of reach of children.  Children sometimes think that medicines are candy.  

Install fire alarms in every room and train children on what to do if there is a fire.

Cover unused electrical outlets.  Children might stick their fingers in the outlet and get electrocuted.

Use safety gates to block access to stairs.  Children can fall down stairs.

Keep young children out of the kitchen when you're cooking.  They could burn themselves on the stove or cut themselves with a knife.

Supervise children near water (bathtub, pool, etc.).  Children can drown in a small amount of water.