Keep playing scenarios to earn your character Experience points as there are certain upgrades and block types that require that your character reaches a certain level before they become available.
Remember you can climb any surface, so feel free to take evasive action by jumping into a pit.
Use trees to place howitzers and rocket launchers on for added range and protection.
If you see a lightning symbol on any defensive object, it's not receiving power.
You can check the radius of a power block's effect by selecting it with the pointer icon.
To mine resources most effectively, place the mineshaft directly over the resource block. This will increase the acquisition rate of those precious minerals.
Make sure you have adequate lighting around your barracks so that your turrets can continue to fire automatically on the invaders when the night falls.
Certain upgrades, weapons and block types don't become available until you've leveled up sufficiently. To level up your character just keep playing through scenarios and you'll gradually earn experience points.
Try to strike a balance between profitability and defense when choosing the location for your barrack. Height is good, as it makes it harder for enemies to assault the barracks, and you also want to make sure you have access to as many resource nodes as possible.
Walls are an incredibly important part of any barrack's defenses. Different block types confer different defensive advantages, so experiment to find one that works for you.
Be very careful when you switch from defensive planning mode to FPS action mode as you will fall directly to earth from wherever you happen to be during this transition.
The crafting system in Block Fortress is built around the special resources that can be acquired from each map type. If you're lacking a certain resource for a juicy upgrade, try playing on a map that specifically offers up that resource, and focus on extracting as much of it as you can.