#1
Is there any specific guidelines that should be followed or is it pretty much just personal taste and experimentation?
#2
Some effects work better in the FX loop, others are better between the guitar & amp.
Delay is usually put in the loop whereas wah or overdrive pedals usually go before the amp.
#3
Wah - pitch effects - distortions - modulation - time based effects(ie. delays)

This is typically the rule of thumb to follow, but you can experiment, moreso with the placement of modulation effects.

Also, modulation and time based effects can usually be put into the effects loop.

But there is no REAL right way, just don't put your distortions/OD in your effects loop.
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