An important communication skill is to simply know what form of communication to use. For example, some serious conversations (layoffs, changes in salary, etc.) are almost always best done in person.
You should also think about the person with whom you wish to speak, if they are very busy people (such as your boss, perhaps), you might want to convey your message through email. People will appreciate your thoughtful means of communication and will be more likely to respond positively to you.