Hi and welcome to the forum! Have you started your wall yet? It may help to share some photos of the wall so our members can give the best advice to you!
well put your set square at 45 to corner of tile and this is the bottom cut , offset the tile by its width and this is second bottom cut . set it out on a board from center if unsure so get equal cuts either side
Every wall /setting is individual!
In general terms you need your vertical and horizontal lines set and maintain them from the start. I’d set out your herringbone dry laid with joint on a flat base first and check the measurements. From a Center line ensure you’ve got good cuts to edges and 100% make sure you follow the pattern around corners. I’d be starting off a tray or bath or baton and working up the wall - vertical alignment is a must!