I am a telecom trainer 🙂
To be successful, you need (no talking about technical knowledge):
1. be able to express concepts and ideas clearly
2. be able to “aggregate” your knowledge and deliver just what’s necessary for your audience
3. listen to yourself when you’re talking (in other words, put yourself in the position of the trainee sometimes)
4. keep your trainees awake 🙂 not as easy as it seems after few days
5. to be humble and accept to learn from your trainees (not as easy as it seems for some)