My wah always goes at the end of the chain. Reason being is that any pedal in the chain ahead of it which increases signal strength(i.e. od's, boosters, dist.) also tends to increase the sensitivity and overall effect of the wah. More gain to the Wah=More CowBell. Wah always comes last for me.
First before drives, and compressors if used. Would put tuner first instead and wah second, but tuner comes second due to fitting it all on my board. Not that it makes much difference to tuning accuracy as long as the wah is turned off.
After octave, fuzz and treb boost for me... but it does sound great after some Od's as well. This is just how I have mine... I guess cause Im right footed ( '= ) and its on the right hand side of my board.