One thing some players find very confusing is combat attachments. I've seen the most experienced player get this wrong, or not even know that they could do this. The silly thing is the rule is pretty much one of the very last rules in the book.
Take a look at a HQ section in any Intelligence book.
Almost every one has something you can attach. Lets look at the Eastern Front Strelkovy. This is a great example. There are 6 groups of attachments here.
There are a couple of things you can do with these. Lets say you take the anti-aircraft platoon.
#1 - You can field them all as one leaderless platoon. Of course they have to start in command, so they would have to start near the HQ or 2iC. Through the course of the game you can attach the HQ or 2iC if you want them to move.
This platoon does not count towards deployment when counting platoons for reserves or platoons in ambush. They will deploy at the same time as independent teams. But are not in themselves independent teams.
They also do not count for purposes of destroyed platoons for Victory Points or Moral checks.
#2 - You can attach them to other combat or weapons platoons. You can attach them all, or you can attach them on a team by team basis. A lot of people don't know this. Using the Anti-aircraft platoon, you could attach 1 each to 3 different Strelkovy Companies.
The catch is they act like transports. They do not count towards your total number of units in the platoon, but they do count towards losses.
However, in the case of the Soviets they do count towards the number of units when calculating the Quality of Quantity special rule.
There are also certain weapon platoons that can attach. For example German HMG platoons or Soviet Flame thrower Companies can usually attach to other combat platoons.
NOTE: You cannot make combat attachments to Support platoons. Sometimes people can forget this in cases like the Anti-aircraft platoon. Lets say your strelkovy takes a T-34 company as support. Well you might think to attach your anti-aircraft platoon to the T-34 company because they are also tank teams. But you cant'