It all depends on what kind of wah sound you want. If you want a subtler sound, put your wah in the loop if you use other effects there, or if you don't use the loop, and use a fuzz/OD in front of the amp, put your wah after that. If you want the wah effect to stand out, like most people do, put the wah in front of the amp as the very first pedal in the chain, before any fuzz/OD effects. You can experiment if you use modulation effects like chorus, delay etc, to see if you like the wah sound being effected by those effects, or having the wah'd signal already going into those modulation effects... I hope that all makes sense.
I only use two pedals, those being my Dunlop CFH Wah and Boss NS-2. I always put the wah before the noise suppressor because that way the NS-2 takes care of any noise coming from the wah when it's turned on (which is usually a lot of noise).