If a speaker knows his audience, he can guess which sense they're most likely to respond to – sight, touch, hearing, taste, smell – and craft the metaphor accordingly.

Whenever one of us says anything to the effect of “and to be honest with you” in any of our conversations (or any of its filthy cousins, like “in all honesty” or “truthfully”), we call that person out.

Using anything like “honestly” in a sentence makes people pause (without really pausing) to think, 'Well, if he's being honest with me now, what about the other three things he just said. Were those dishonest?' And thus, this little verbal snafu decreases message value – not only are people considering what you just said ('Now he's being honest'), but perhaps more importantly, they're spending time thinking about what you just said, rather than paying attention and being invested in your originally intended message.

Honestly, pay attention to this in your daily activities. I promise you'll be surprised how many people use this term – and how pervasive it is.