Motivating salespeople is easy, but most managers or business owners 'don't or won't' take the time to do it.
Sit down with your sales person, find out from THEM, what they don't have enough of NOW, that they want in the next 6 - 12 months. Break it down into smaller monthly pieces and build your compensation plan around it.
Motivation is an internal driving force that will cause actions to happen with the goal of accomplishing an end result.
You can't motivate someone else, but you CAN create a compensation plan that will give incent someone to work to accomplish something, and in the end, get what they also want.
That is then a win/win.
But most managers or owners, just raise the salespersons 'quota' hoping that will get the job done.