You can increase your chances of being understood by doing the following:
- Face the person you are speaking with. This helps in many ways, nonverbal cues, body language, and reading lips.
- Take breaths between syllables or words (depending on the length), since in most cases the lung/air capacity has already been compromised.
- Slow down your rate of speed when you talk. This will help keep you from running sounds/words together.
- Pronounce all sounds as clearly as possible.
- Use short sentences, so you have to think about what you want to say and then think what is the best way for you to be able to convey what you want or need.
- Avoid talking over background noise.
For me personally, background noise is the worst. With the low volume I have, this is a very difficult thing to work around. That is when a communication board, sign language, or even writing it down is useful.