How to connect properly the effects at the front (between a guitar and an amp) and in the amp FX loop?

Many guitar amps features the FX loop for connecting the effects. Usually it is the serial loop (see the dictionary) and for sure the delay and reverb type effects should be connected to such loop. In case of using the stompboxes connected to the looper it is needed to use together with the GSC-2/3 the looper controlled via MIDI e. g. Midi 4x LOOP M4L. Thanks to that we avoid the grounding loops problem and it is possible to place the effects near the amp.