If you are using your twitter profile to promote or market an event/product/business or what have you, I guarantee you are posting like crazy, blasting out scheduled tweets every day, maybe even every hour. Don't get me wrong, that's a good way to get details out to the world, but what if no one is actually reading them? And if they are, are the right people reading them?
One way to know for sure is to send direct messages to the people who fit your "target audience" profile. A direct message will show up in their twitter inbox and only they can read the message. It's more personal, and it garauntees that they will actually read it, whether they want to or not (unless the person completely ignores messages sent to them, which would be wierd).
This may be a little more time consuming, but probably more effective. While the twitter platform only allows you to send one direct message at a time, there are ways around it. I read how to send direct messages to multiple twitter users through an application called TweetGuru. Very simple, and it will save you time.