Wash jars well in warm, soapy water and rinse thoroughly. If your recipe calls for a processing time of less than 15 minutes immediately before filling them.
Alternatively, place the jars on a baking sheet and dry them in an oven at 170 C (340F) to sterilize for 1 hour. Fill the jars while they are still warm to prevent cracking. The tops for the jars should be boiled for 10 minutes just prior to use.