** If you are doing a parkrun then start at the front that can save you many 5′s of seconds especially at busy ones like Bushy. With a 1000 people at Bushy Park starting at the back will cost you AT LEAST 20 seconds (I’ve tried it and timed it).
All the suggestions are starred:
*** 3 stars. IMHO it will work
** 2 stars. It might work
* 1 star. Can’t hurt
X 1 cross. It CAN hurt if done wrong.
All 50 tips are shown here as a series of posts : http://the5krunner.com/tag/how-to-get-a-5k-pb/ or on twitter using #howtogeta5kpb. They are all SHORT-TERM tips that will work in the next week or so with varying degrees of success.