Answer:
This is a sophisticated issue. Tone is actually in the domain of speech; it is how the voice indicates the attitude or feeling of the speaker, such as a mournful tone, an angry tone, a respectful tone, etc. These tones of voice may merely show the speaker's state of emotion, or they may show the speaker's attitude toward the listener. For example, a person may speak in a happy tone without it having anything to do with the listener. Or the speaker may have a particular attitude toward the listener or group of listeners, and it shows by his/her patronizing or "superior" tone, a warm tone, or a pleading tone, etc. People will also adopt certain tones when they talk about certain subjects.
In a written work, where there are characters speaking, you can usually catch their tone by reading their speech aloud (after look at what they are probably feeling at this point and to whom they are speaking and why). Actors do this to figure out how to deliver their lines. Repeat the oral reading, noting the words or phrases that especially stand out as indicating some feeling. In an otherwise neutral, unemotional speech, look for words or phrases a bit different from the usual options. This illustrates one way of using language to communicate tone. The author can also put in words like Alas! and Hooray! and You fool! to communicate tone.
When reading a passage which has only the author's "voice" in it, try reading that aloud as well. You might do some research into the author's background, beliefs, pet peeves, and hangups. The tone will be an attitude or feeling directed either at the reader or at the topic. (Or possibly at oneself, as in writers who poke fun at themselves.) Try reading it aloud different ways. Even better, get with a group and try reading any work aloud different ways by different persons. A great way to take time off from the computer and use your voice instead of emoticons.
Keep this in mind: all literary forms were once oral. So there is always some kind of tone there that you can bring out in oral reading.