I was taught this useful bit of advice the other day from a very experienced WFB player with my Empire infantry.
First I'm sure we've all learned the hard way is that not all infantry blocks is created equal. For instance a 40 unit horde of White Lions of Chrace is very different from a 40 unit horde of Empire Spearmen. One is suppose to kill every living mother loving thing out there for the price of 520 Points while the other is cannon fodder for the lowly price of 200 points.
Now if the White Lions Charge the Empire Spearmen most likely the White Lions will wipe out the Empire Spearmen in one turn. So whats the use of having those spearmen.
The guy told me to ask myself this question what is the purpose of those spearmen, Horde blocks exist mainly to either destroy the other guy or to hold his killers in place while the rest of your army kills everything else. In my Empire Spearmens case I should use them in a way to maximize survival while facing those White Lions so I might be able to delay them for one or two rounds so I can bring other units to attack the flank or rear of that unit.
What I should do first is instead of going 10 wide x 4 deep go 5 wide x 8 deep blocks. Reform the spearmen so you only show 5 men to his 10 men when they charge me. The key is he is only now in contact with 5 of your men instead of 10 in the front. So now only 7 of his men in the front and the supporting units in the back can strike instead of all 10.
So lets do the math. Instead of 40 attacks you've just reduced his attacks to 28. 3+ to hit mean 18-19 hits. 2+ to wound reduces the total to 15-16 wounds. Its not much but it is definitely better than 40 attacks which gives 27 hits and 23 wounds. Say you've taken 15 wounds you've got 25 men left. Which means 5 ranks of 5 men to his 4 ranks of 10 men. You have one more rank than your enemy and Steadfast rule comes into place which means you take your break test on your Unmodified Leadership.
Your Spearmen just locked those White Lions for one additional round of combat. Now you might be able to gather other units to charge his flanks or maybe have some skirmishers who can charge his rear rank, next round those White Lions is Surrounded and you've got a decent chance of wiping out his Super Infantry block.