The first thing is to talk from the point of view of your audience, since it's their perspective that determines what they hear. For this, you first have to know your audience, and the key to understanding your audience is to listen to them. Strangely enough, in order to communicate effectively to others, you first have to listen to them. You then need to get out of your own head and really imagine that you were them, listening to your words.
The second thing you have to do is to consider the emotional impact of your words on your listeners. Since people interpret what you say through emotional filters, and their emotional reactions to what you say are going to drown out their rational responses, you need to think about the emotional land mines you might be stepping with what you say.
The third thing you can do is to get help from other people. If you are not good at figuring out the emotional impact of your words on others, have a friend or colleague help you, since an outside perspective often helps identify things you've missed.
Even with all of these steps, there is no certainty that your words will be understood as intended, but it's a matter of probabilities and you can make it more likely. So in the end, though what the other person actually hears is still out of direct control, it is up to you to construct your messages carefully and communicate from the other person's point of view.