There comes a point when maybe you’ve made one call too many. But how do you know when that is? Sales trainer Adrian Miller wrote a great post on her blog, in which she says, “It is instrumental to understand where that line is drawn between persistence and nagging. This requires the ability to recognize when a request or a question is self-serving and doesn’t offer a benefit for the person being queried. Persistence is a good thing. However, to be perceived as persistent, yet not a nag requires the mastery of the following skills.”

Here are Miller’s tips to ensure you don’t cross the line:

Respect
Persistent salespeople are very aware of their prospects’ and customers’ time. They respect other’s time constraints and understand their priorities most likely don’t include listening to lengthy sales pitches.

Value
When reconnecting with someone in a persistent mode, it’s absolutely necessary to have something of value for them. Don’t be tempted to just “follow up” or “check in”. Instead, have information, an invitation, or an introduction to present to them. You’ll be deemed far less self-serving by bringing something of value to the table, and they’ll be far more receptive to your repeated attempts to get them to buy something.

Sensitivity
Knowing when to rein it in is essential. Even though you can’t lose what you don’t have, you can irritate prospective customers so much so that they will nix you from all forms of communication. Once again, respect and consideration are the rule.

The best salespeople are skilled in remaining persistent and not getting discouraged while never crossing the fine line between being a nag or nuisance. Being able to do this is one of the most valuable skills that a sales professional will learn and it requires ongoing practice to refine and master.

Adrian Miller is the President of Adrian Miller Sales Training, a training and business consulting firm delivering sales-level performance training and executive-level business development consulting. A nationally recognized lecturer, she is also author of "The Blatant Truth: 50 Ways to Sales Success".