The order, and why

First, because it wants the raw signal to read pitch from, and because muting here kills everything downstream at once. It is the only pedal whose job is easier the less has happened to the signal.

Early, so it shapes the plain guitar and the drive after it responds to that shape. Put a wah after a distortion instead and the sweep sounds flatter, because the distortion has already flattened the dynamics the filter would have moved through.

Near the front, where the dynamic range is still wide enough to be worth squeezing. Some players put it last instead, to even out everything the board has done rather than what the guitar did, which is a real choice rather than a mistake.

Ahead of the other gain, and for some circuits ahead of everything. A vintage-style fuzz has a very low input impedance and is voiced around loading the guitar's pickups directly, so anything buffered in front of it changes what it hears.

After the fuzz and before everything time based. Distorting a signal and then delaying it keeps the repeats clean; delaying a signal and then distorting it drives the repeats and the dry note together into one smear.

Either side of the drive, and the two do different jobs. In front, it changes what the drive clips. After, it changes the finished sound. Most boards that own one put it after, then use a second in front when they want the drive itself voiced.

After the gain, because the gain is what made the noise. A gate ahead of a high-gain drive is closing on a quiet signal and then handing the silence to something with enormous gain, which amplifies the hiss it was meant to remove.

Position is a genuine choice. Before the drive it changes how hard the drive is pushed, so it doubles as a gain control. After the drive and before the delay it fades the level while leaving repeats to ring out. At the very end it is a master mute.

After the gain and before the delay, so the delay repeats a modulated signal rather than modulating an already repeated one. Reversed, the movement gets applied to the echoes as a block and the effect smears instead of swirling.

Near the end, repeating a signal that is already finished. Anything placed after a delay processes each repeat again, which is occasionally the point and usually a mess.

Last, because it is the room. A delay into a reverb puts each repeat in the same space, which is what happens acoustically. A reverb into a delay repeats the room itself, which does not.