*X Insoles. Many of us have one leg longer than the other for a variety of muscular/skeletal reasons. You can’t change that by the weekend. BUT if one leg is a few mm shorter than the other an extra insole will balance your legs and might give you a bit more power. Or it might distract you from the balance you have already got used to and to which you have already compensated for. This one is probably not worth the risk for the weekend.
But you should find out if your leg lengths are different as this may also eventually lead to injuries. The cause could be skeletal or it could be flexibility/posture related. Small differences eg 3mm should be ignored.
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.