The lance formation is integral to all Bretonnia Generals thinking. It is indeed the key to success for a unit of knights and as important as their armour save and charging first into combat.
Bretonnian Knights can field units with a front rank of 3 but a lot more than 3 knights get to fight in the melee.
In fact a front rank of 3 with 1 rank behind will allow 5 of the 6 knights to fight. 3 ranks will allow 7 knights to fight out of the 9 in the unit.
This is because those models on the flanks also get to fight. This, presumably is to emulate the old wedge formation and to tale into account the large points cost of units of knights.
Note that standards and musicians do not need to be positioned in the front rank.
The lance formation is key to the Bretonnian charge. Units need to be bolstered with Lords, heros, damsels and magic items to try to ensure that the enemy is taking a break test in the 1st turn.
Bretonnians become far less effective in longer drawn out fights because they do not benefit from their +2 strength lance after the charge. Also, they are very prone to being outflanked amd charged in the side (and frequently the rear aswell).
To counter this lance formations need to be small (mainly 6 models strong in a 2000 pt game and definitely no mre than 9 strong)
You should also keep a unit in reserve to respond to developing threats (if your knights get tied down) before they become a problem.
Keep your eye on any fast moving units that the enemy has, especially flyers.
I will be writing some tips on how to bolster knights and especially including those fine damsel and prophetess ladies in your units. They are well protected by the knights in the initial rounds and can come in very useful in the fight.
Watch this space.