How do you treat customers when you place them on hold? How long does it take you to get back to them? Do you have an on-hold message or music they can listen to? Are they left on hold for long periods of time? Did you put them on hold because you felt an incoming call was more important than they were?
Ask yourself this question. Is it ever really absoulutly neccessary to put a customer on hold? The answer to that question is NO. You're most likely thinking sometimes it can't be avoided. I say yes it can be avoided.
The solution is this, call them back at a later time. If you need to research their account or to take another call, simply ask if you can call them at a later time.
Your on-hold methods are a part of marketing. You'll be surprised how many customers will appreciate a call back as opposed to being placed on hold.