General

- Play on Easy or Normal at first, the difficulty ramps up pretty quick after the first couple stages.

- There is no auto-save. Make sure you save early and often.

- The game expects you to switch weapons regularly, otherwise you'll quickly start running into ammo problems.

- Maneuverability is life. Try to always have room to strafe and somewhere to retreat to.

- On that note, watch your step, the game is an asshole about bottomless pits.

- The shotgun has much less spread than you'd expect, but a fair bit of drift.

- Turning on or off objective hints is a personal choice. They're not too difficult to find with the brightness up at a decent level, but the levels are large enough that if you miss one, it can be a bit of an ordeal to track it down.

- The free health/ammo refills at checkpoints are tied to that specific point. Don't feel bad about using them, but consider saving them if you think you might backtrack to them soon.

- Every level has one 'trap' checkpoint that takes you to a fairly tough arena fight, so try to keep that in mind. Bright side, find them all and you can assemble the ultimate weapon.

Cheats

- Different versions of the game have their cheat codes changed for whatever reason, On the Steam/GOG release, the master cheat is BEWAREOBLIVIONISATHAND.

- You can play pseudo-co-op by entering multiplayer, then using the level warp cheat. Fair warning, this will completely disable checkpoints, so you may want to consider also turning on Infinite Ammo.