When making jams and preserves you obviously need to sterilize the jars. After the jars have been sterilized do you need to use them straight away or can you sterilize them in advance and keep them for when you're ready to use them?
You should be packing the jars while they are still hot, for rawpacked or hot-packed products. For hot-packed products, this helps avoid the risk of the jar breaking.
For great instructions on how to can at home, see the National Center for Home Food Preservation.