When hovering over huts to see how many followers are in it, there's two bars on the left (green and red). The green bar indicates how much progress there is for creating another brave. The red bar indicates the progress on upgrading the hut to the next stage.
Sending a couple of firewarriors into a hut will allow them to be hidden to the enemy. This can help fire unexpected fireballs into the shaman to kill her on her attacks.
This is similar to the shaman when she is in a hut. However swarm can scare followers out and cause them to go out of control.
To kill a shaman that is in a hut by casting lightning on the hut then again on the exit of the hut.
The dismantle trick is used to quickly gain extra braves without having to wait for the period of time it takes to produce one automatically.
Manually upgrading is a fast way to upgrade your small huts to the next stage. You can manually upgrade a hut by commanding a brave to pick up wood and place it on the hut entrance. The red bar should increase a notch.