Hint: Easy kills
Throw a remote mine on an enemy. If it hits, they will scream and run around instead of shooting you. Let them run around and eventually they will try to find guards. When they do, detonate the bomb to get two or more frags for one.

Take out your pistol with the silencer when you see a guard. Press R1 as fast as possible until the guard is dead.

Hint: Avoid detection
In the single player game, there are two locations where you have to be stealthy. One is when you pretend you are a businessman and the other is when you have to pretend to be a scientist. To make it easier to avoid detection from guards or other pedestrians, always look down or away from people. No one will learn your identity until you look them in the face.

Hint: Getting items
When low on energy, kill worker doctors and even Red Faction men to pick up more health and Environment Suits.

When Hendrix first starts talking to you, go down the catwalk away from the
APC. There should be a tunnel that leads to a miner and guard fighting. Shoot that guard then shoot the one at the elevator. Stand in front of the elevator and face the wall behind it. Look up slightly to see a hole. Enter the hole and at the end is a pond or lake. At the bottom of the pond is a miner's body, health, and an Environment Suit.

Hint: Saving ammunition
When you have remote explosives, do not use up ammo for your other weapons. It only takes one to a few remote explosives to take out enemies. When you start the game and get to the part where you see the four troopers and the enemy APC, throw a bomb down by the APC. Detonate it and the bomb will blow a huge hole in the ground. If done correctly, the APC will fall in and explode when it hits bottom. Take advantage of the geo-modification of this game. This also works with groups of enemy soldiers.