Dave Barlow Guitar Video Blog
Locking tuners seem to be the retrofit rave these days, yes they can help with tuning issues but make sure you have checked the obvious things first like, trem, nut, crappy strings and loose parts etc.
Here I show you how to fit some inexpensive (but good quality) new locking tuners to your favorite axe, I also point out some pitfalls when purchasing (mainly due to making sure you check measurements before purchasing).
I purchased my locking tuners (or machine heads) from here: http://axetec.co.uk/guitar_parts_uk_060.htm
They always have the specs and measurements on the same page which takes the guesswork out of purchasing the right tuners.