I've written a number of columns about prospecting--about selling from the top down, about building relationships, about being creative, about being tenacious when the going gets tough. These are all important points--especially the one about being tenacious. But there's a fine line between being persistent and being obnoxious, and salespeople sometimes worry they're going too far and pushing themselves right out of the sale.

Here are some tips to help you persist without annoying prospects:

Deflect the resistance. If you keep calling and the customer keeps putting you off, let your customer take the lead. Say "There seems to be something I've missed. Is there any information I need to know to better understand the fit between our services and what you're looking for?" Most customers would rather help you make the sale than feel like they've been manipulated into it.

Learn as much as you can about the customer. Gather information that has nothing to do with your goals or objectives, but rather with theirs. Ask yourself "How much do I know about this customer? Did I demonstrate to him that I'm willing to put in the extra effort to earn his business? Do I know anything about this customer on a personal level, like interests or hobbies that I can relate to?" Finding answers to these questions is a great way to build a bond and lower the annoyance factor.

Stress your belief that what you're selling has value for the customer. The stereotypical salesperson who turns customers off cares only about her own commission and doesn't care about the customer at all. Customers who feel like you have their best interests at heart will actually appreciate your persistent concern.

Use humor. This is a tough one, because what's funny to one person may not be funny to the next. Often, poking fun at yourself can break down barriers. You might joke "It says in my sales manual that customers say no six times before saying yes. This is my seventh call, and you're still saying no. Didn't you read the manual?" It's difficult for a customer to get mad when they're laughing at what you've said.

Don't get desperate. At the end of the day when you're ready to go home, make a few more calls. The more activity you have going on, the less likely you are to be desperate to make a sale. When you're desperate, you can easily cross the line between being persistent and being obnoxious. That's when customers know you're interested only in getting the deal. When you have enough activity going on, you can make the decision to move away from a sale that doesn't match the customer's needs.