How can I prevent my toddler from choking on toys?

Your toddler should. Not have access to toys that are so small that s/he can choke on them. Please ensure that s/he only plays with toys that are safe for his/her age level.
Safety. You are in control. The environment needs to be safe. And, your child needs supervision.
Keep small toys away. A good rule of thumb is: if it can fit through a toilet paper tube, then it is a choking hazard. Check all of your toddler's toys and put away and lock up any toys that have parts small enough to fit through a toilet paper tube. If they get upset because a toy is now gone, don't worry, they will get over it. You are in charge.