Here are just a few general tips. I hope you find them useful.
1. The bad guys aren't immune to each other's guns: If they get hit by one of their comrades they will forget about you and turn on the guy who shot them. This may not be the case with some monsters. Most of the bad guys, however, will start shooting whoever shot them and you can just sit back and watch.
2. Don't waste ammo: For instance if you can barely see an enemy because he is too far away, don't try to shoot him with the shotgun. This is because the shotgun looses force with distance. Wait until you are closer, then blow him away.
3. There is a time and place for every gun: Do not whip out the BFG 9000 on a group of Zombie Privates. Only use the big guns on the big guys. If you use them on the little guys, you may not have enough ammo left to take out something big.
4. Play it safe: When entering a new room, run in quickly and run back out. If you don't hear a groan, there will not be any monsters right next to to the door. If you want to play it extra safe, fire a shot as far down the room as possible. Wait for them to come to you.
5. Listen: The Imps snort. The Mancubi have their own weird little battle cry. The Former Humans and Former Sergeants pretty much sound like they did when they were still on Uncle Sam's payroll. Each time they spot you, you'll hear some sort of alert. Use this time to figure out where the worst enemy in the room is, and start blasting.
6. Learn to maneuver: Practice being ultra fast on your feet. If you can dodge the enemies bullets you've got it made. Strafing and running are two things that are absolutely indispensable. Try this: I beat the first level on Nightmare; no codes, just the Chainsaw. And I didn't get hit. Gloat, gloat, brag, brag.
7. Use "circle-strafing:" If you use the mouse, you can do something called "circle-strafing." Just press forward on the keyboard and left or right on the mouse at the same time. If you insist on using the keyboard (like I do) you can do this by switching off running forward past an enemy, and going backwards while turning.
8. Practice makes perfect: Play Doom II whenever you can. Play, play, play, and then play some more. And when you feel you just can't face another pesky Cyberdemon, don't. There are other things in life, you know.
9. Have fun: If you find yourself getting bored, save your game and then just go wild. Blow away everything you see with the biggest gun you have.
10. Don't use the cheats to beat the game: At least not the first time you play it through. Beating the game with cheats turned on takes the fun out of it. Only use cheats on the levels that you have mastered. That way you can find more secret areas and you aren't spoiling anything for yourself.
11. Disable extensions: Using the Extensions Manager included with System 7.5.x. Disable everything but Quicktime, Quicktime Powerplug, Sound Manager, and the Sound control panel (all of these are needed to play music). If you don't have enough memory to play music without RAM Doubler or virtual memory anyway, just restart holding the Shift key down. This will disable ALL extensions.
12. A tip for modem play: Disable flow control, data compression, and error correction on the modem. To do this, type AT/N as the modem string.
