My mistakes when new included

a. Not giving arrows to my players or giving them the wrong ones
b. Not using whole pitch pressing when attacking w/ superior team.
c. Focus passing down the right flank through a low 3 star player, instead of through my 4/5 star midfielders during the CL round of 16 of season 2.
d. Changing tactics during a live match to an illegal formation (DL got injured and I replaced him with a DC I think, leaving me w/o anyone on the left.