Power Relay Towers
Without towers nearby, your CyberPod isn't going to have enough energy to keep up with energy demands. Creating a good network of towers so that you always have the maximum power to work with, is a key element in the game. With power your shields can regenerate. With more power, they can regenerate faster.

The more energy-intensive modules your CyberPod is carrying, the more power input you will need. Any module that lights up, such as Stealth, Shield Piercing, Phalanx, and Automated Repair, is using more power. As long as they are lighted (highlighted on your list of modules in the upper right corner of your screen), they are sucking power from your battery. You need power input to keep your battery charged.

If you are low on power input, you can lessen the drain on your battery by deactivating some or all of the modules that are currently on (highlighted) in your module list. Press the number key corresponding with the module bay number to turn it off. To turn it back on, press the number key again. Modules such as Automated Repair should be off when they are not needed. When the power supply from your battery drops to nothing, activated modules will start shutting themselves down automatically. In this case you are probably in trouble. If you get into a firefight, your odds of surviving are greatly reduced. Get back to your power grid, or order your Raven to drop some power relay towers in your area.

Ravens and Supply Drops
Ravens are great. They give you stuff. Their most important function is dropping power relay towers. They  take time to navigate to the drop zones, so don't order 10 towers, then order a repair module, and expect the repair module to be delivered immediately. It may be quite a while before the Raven gets to your order.

Dropping supplies in the middle of a firefight can be a great way to turn the tide of battle. However, keep in mind that anything you drop into the area may be picked up by any CyberPod, including the enemy. You might find yourself facing an opponent who is blasting you with your own munitions. If you are really in need, don't hesitate to call for a drop, but keep one eye on the drop zone as well as your enemy. Try to keep him clear of that area.

Stockpiling is a good strategy in some missions. To do this, you order little piles of grenades, rockeyes, repairs, or other expendables in a few nearby places, or in a safe zone. When you use up your supplies you run back and load up with what you need, without having to wait for your Raven. Just keep in mind that if your enemy runs across your stockpile, he may decide to help himself.