1) Decide whether it's an A or B race for you. If it's not the key race of your season you can see it as more of a stepping stone to your main goal. If it's just a B race you'll feel more relaxed and you won't need to taper for so long before the race.
2) Set yourself not just a "best case" target but an "OK" and "acceptable" targets. That way you're mentally prepared if the race doesn't pan out exactly as you want.
3) If it's possible check out the race course beforehand. Then close your eyes and visualise yourself at key landmarks during the race. You're running strongly. You cross the line, smiling, your arms raised.
As Paula Radcliffe writes in her book "How to Run"
"I use this technique (visualisation) a lot in race preparation. I visualise how I might act in a few scenarios that could unfold during the race (always calmly and in control); and I consistently conjure up a vision of myself crossing the finish line in the best possible shape and form."
4) Wear red. A German study found that athletes who wear red perform better than those in other colours. This may be because wearing red makes people feel confident and may also intimidate other competitors.
5) Try to relax before and during the race. This might be meditation or whatever works for you. You can't run well if you're not relaxed. Look at Usain Bolt and Haile Gebrselassie on the start line. They're joking around and grinning - then they go on to win!