#1: Speak slowly.
Most people speak too quickly, especially when they are nervous. People are more likely to be nervous when in court or in a deposition, and this is when court reporters are trying to take down every word that you say. Therefore, if you would like the court reporter to take down every word that you say, speak slowly. Chances are that you are probably speaking more quickly than you think, anyway. This rule is even more important if you are using medical terminology or other specialized terms which the court reporter is not likely to encounter very often.
#2: Read even more slowly.
People read much more quickly than they typically speak. If the document that you are reading is important (and it probably is, or you wouldn't bother to read from it), then you should slow down while reading to make sure that the words are on the record.
#3: Spell difficult names & specialized terms of art.
If your name is Smith or Jones, you don't need to spell it. If your name is more complicated, spell it for the court reporter (and don't forget to spell slowly). The same rule holds true for medical terms or other specialized terms. If you would like the transcript of the hearing/deposition/etc. to have correctly spelled words, and those words are not in the lay person's vocabulary, spell them for the court reporter.
#4: Don't go off on tangents.
If the court reporter asks you to repeat something that you have said, do just that--repeat what you said. Do not go off on a tangent explaining the concept or background story to the court reporter. The court reporter was not asking you to repeat yourself because s/he did not understand what you were talking about, but only because s/he did not hear or understand the words that you said.
#5: Do not interrupt or speak over another person.
A court reporter can only take down one speaker at a time. When people talk over one another or interrupt each other, the record becomes muddled and may even be missing some of what was said. Wait until one person has finished speaking before you speak.
#6: Answer out loud, using real words.
Do not nod or shake your head, as a court reporter can only take down verbal responses. Try to minimize mmm-hmm, hmm-mmm, uh-huh, and huh-uh, as these can be taken down by the court reporter but are open to interpretation. Use "yes," "no," and other real word verbal responses.
#7: If the court reporter is marking an exhibit, do not speak.
When the court reporter's hands are off of the machine, s/he cannot take down what is being said. Therefore, when the court reporter is marking an exhibit (i.e. writing on an exhibit sticker and placing that exhibit sticker on a document or other type of exhibit), s/he cannot possibly take down what is being said, and attorneys and parties should not speak at this time.