Weigh two pounds of chocolate on a scale. Some bonbon and truffle recipes written for the home kitchen will call for one pound of chocolate, but my experience has been that one pound of chocolate is not enough to hold a temper. I recommend always using two pounds of chocolate, unless the recipe specifies more.
Here's why: tempering chocolate requires precise temperatures. When you only use a small amount of chocolate, it will cool and thus harden quicker than you are able to make use of it. You want the chocolate to hold its temper for as long as possible, and using more chocolate enables you to spend more time dipping and enrobing your confections and less time worrying about bringing the chocolate back up to the proper temperature.
It should be noted that any leftover tempered chocolate can be reused and retempered at another time. You can keep the tempered chocolate in the bowl and wrap it in plastic wrap. Alternatively, you can transfer it to a baking sheet with a silicone nonstick pad and allow the chocolate to harden before breaking it into pieces and storing it in a resealable plastic bag.