Another general communication skill is adaptability. A person needs to know how to adapt their method of communication depending on the recipient and the circumstances. This will help to dictate what tool is used to communicate with. For example, using Skype or email or letter or the telephone. To be able to adapt you need to know your target group or audience, this will have an impact on the way you go about communicating to make sure that target audience is engaged.
Another skill would be tone of voice, even if someone can't see your body language and or expressions they can still tell your mood by the tone of voice; for example if someone was angry at you over the phone their voice would be perhaps louder and more aggressive than someone who was giving you good news. Tone of voice also has an impact on questioning as with the way you construct your sentences. There are three different types of questions which are depicted by the way you construct it. For example a direct question would address you or a specific person for the question, so if someone said your name before asking a question it is a direct question. Direct questions can be also be open or closed.
Grammar and spelling are important written skills because you can't write full letters as one big sentence in one big paragraph. In order to be able to communicate effectively with written skills you need to use the correct spelling and grammar so it is easy to understand and follow the text.