I've seen a good number of threads asking which is the best knife to buy and I have wasted money changing from one brand to another because all of them got blunt quite quickly and I could never get any of them really sharp again . Messing around with a blunt knife can be really frustrating at the end of a good day's fishing .
The technique shown in this link is amazingly effective . At first it looks like a lot of hassle but is no bother once you've set up the boards ( I use a slab of slate , anything firm and very flat ) . Get the wet-and-dry from an autofactor / body shop .
Scroll down past the first few posts then you'll see the good one , with pics .
http://www.rivercottage.net/forum/the-r ... ng-knives/
Good luck