Play with keyboard and mouse - makes hitting things much easier. Redesign all mechs to have max armour. For most of the campaign bringing as many SRMs to the field as possible is good. Focus fire with your lance mates - makes them much more effective. Remove JJ - useless. LBX10s are great. Remove useless single LRM 5s and 10s from most things - put a lot of lrms on mechs with good quirks - Archer, Longbow. Keep moving, ideally always at least 45 degrees to your target