In training, never be afraid to ask questions of your coach, they may be assuming that you already know something. Try to get as much information about your event as possible. Be positive in training and competition - you never know what you can do until you try. Don't be easily satisfied - always think 'I can do better' and go away and work harder
Keep a log of all your training and competition. If your performance was particularly good or bad, ask yourself WHY. Could I have done better? If it's raining, you still have to train - you might not be so happy with the results, but the weather might be worse tomorrow. Missing training is like dropping out of a race. Once you have done it, it is so much easier the next time. This is not to say that you should train every day. You must make sure you get adequate rest and sleep. I personally always had a "fun run" once per week when I would try ( I was never very good at it) to sprint for 100/200 metres half a dozen times in a 5 mile run. I also gave myself a rest day prior to a major race so that I was refreshed and raring to go on the big day.
If you are going out for a long run, or a long race, make sure that you go to the toilet before you start and know where you can stop if the need arises.
If running in a distance race, try to position yourself in the middle of a group. NEVER AT THE BACK. If someone puts in a kick, by the time you are able to react, there is 4 or 5 precious yards between each individual in the group. This is the sure way to get dropped off, and once this happens, only the very great athletes get back.