Who does 1 V 1, Stalker's 51st Yorkshire used to do it, and they where bloody good at it. I bet many regiments would like to do it more often, its just hard to organize these as normally a regiment A* want a private lb with regiment B* and regiment B* doesn't want a lb with them because they and their officers know that they will lose badly. Also different aspects that makes us realize that we're just a bunch of un-civil-ish humans.
Tips for COs and NCOs, before you allow a fresh recruit or cadet into a line battle, make sure he knows which one of you is the officer, this saves a lot of time, you also wont get asked questions like "Which one is the officer, I thought its him * Random Skirm* so I formed up on his right as you've said.".. Yes, That could and it has happened before. Also, never divide lines by ranks, so for example 3 lines, 1 recruits-cadets, 2 Privates-regulars,3 fusseliers- Kingsmen, this will only make line 1 be terribly bad and very hard to lead.. also then lets just say line 3 will get shot down by two over lines and arty and there's your elite gone, its all up to the crazy experienced-ish and un-experienced members, round lost.
For actual event tips and tricks.. well, never walk into a line that's your size and its also aiming straight at you, I followed that rule and my lines where pretty beastly.