Since I have insomnia, let's go with these good-intended tips...
#1
Pure BS
#2
Pure BS. It didn't work in any UFO game, in OXCom it makes the aliens angrier and more prone to suicidal maneuvers, usually involving high explosives.
#3
Use the biggest, most accurate, longest-range weapons to win. I'd never think of that! It works, naturally. Massive damage always works.
#4
Technically true, but impossible to implement in the field other than in a very general manner. Too many unknowns to win by maths. Sure it tells you to leave full TU if you want to have bigger chance of shooting first, but the moment you start relying on your Reactions alone, soldiers start dying. Not every shot hits. Not every hit kills. You might have several people crowded in a defensive position. Said alien can have a grenade...
Reactions are for 2 things: 1. some people prefer risks associated with opportunity fire over the risks associated with storming UFOs/Access Lifts/other tight spaces, possibly infested with chryssalids (not an insensible approach). 2. Desperate Measures (a huge topic unto itself...)
#5
The fact that you think you're facing the alien doesn't mean its shots will always hit front. I'd rephrase it: if all else fails, try to face the alien with your last TUs, the armor is always thickest there, plus you will die like a man. Actuallty TFTD armors have a critical weakness; very high frontal armor offset by the fact that some shots will inevitably hit your sides.
#6
Yes the reapers are weak to Incendiary, but a Heavy Cannon HE shell is a guaranteed kill while Incendiary isn't. Cyberdiscs can be killed by Heavy Rockets but actually are better engaged with lasers or plasma (too heavy armor for your puny grenades). Or if you lack anything that powerful, fire kills them over time, and stun damage takes them out quite fast too. Why kill stunned mutons? Lobsters are very, very resistant to everything but Sonic (Massive Damage) and melee (stun works too). Melee is the way to go with them. Apoc turns into Easy Mode when you invent gas grenades, especially against humans who don't have any resistances. Shooting them with needless is of course possible but pointless in the light of the above. Unless you want to train reactions or whatever.
#7
True, but the odds of these things happening are astronomically low. You either shoot everything and a kitchen sink at these Brainsuckers or suddenly have a soldier braincontrolled. It's much more often (still rare) when Brainsucker's attack simply fails.
#8
No, it's neither realtime or radar. It counts alien score, generated mostly by landings and completed missions. Your craft will usually arrive post-facto and fail to catch anything. It might stumble upon the next wave, but the chances aren't high. The graph is good for occassional sweeps to find alien bases, though. You COULD watch the alien graph every 30 game minutes for any changes and able to use it pretty well to detect UFOs, yeah... thanks but no thanks, there are better things to do with one's life.
#9
As there ever was an area where you shouldn't expect aliens 
But yeah, Mutual Surprise is the way to go. Just don't forget that running away counts as "doing something" and unless there is cover 1 tile away, the alien is going to fry your ass (assuming your main force doesn't take him out as they should).
#10
Use blaster bombs to win. Yeah, great tip As one of the veterans summed blaster "tactics" up, "nuke large rooms first". Actually it's easier to kill your own squad with Blaster Bombs than to die from alien fire once you have a ready supply of these beauties. Btw you usually need to catch Commanders alive, and panic can be easily raised by killing large amounts of low-ranked aliens in a small amount of time...
#1
there does appear to be plenty of versions in which it does not work. I don't know which it works on necessarily but I did it most back in the original DOS version of X-Com: UFO Defense (the USA release) on an IBM 486 with Windows 3.1. I don't have this version anymore and I can't find an authentic one anywhere. If you have one, let me know! I've been searching for the original sounds for a long time now!
#2
This might be a case of apophenia, but there have been plenty of times I have seen one running toward my soldiers until a shot was fired, at which time it immediately headed in a different direction or wasted time units in place. It has happened most commonly with Tentaculats (TFTD) and I think it has happened with Chryssalids (UFO). I've also seen a handful of other melee terrorists do this, like Reapers or Hallucinoids. I haven't seen enough to confirm it but it seems to work. Alternatively, they might be responding to greater numbers of soldiers in one area, which may appear to be them responding to weapons' fire because of the increased chance of reaction fire. I don't know. I'll keep trying it.
#3
Most people wait until plasma beams to shoot down the larger UFOs at all, not realizing Avalanches do the trick pretty well. I took a long time to realize mediums go down easily with Avalanches, and I had no idea that they outrange even Battleships. This means you can indeed fight these large ships in the early game with just interceptors. This is a valuable tactic for before you have completed more advanced plasma research.
#4
"Impossible" is putting it rather harshly. It would be an opinion to say that it is difficult, one I would partially agree with. Most aliens have pretty high reactions, but if you get soldiers with high reactions and are careful how many time units you spend in front of aliens, you can dramatically reduce the times they take reaction fire.
#5
No rephrasing is needed. Sure, it's possible to get the sides hit, but then it's also possible for a Sonic Blasta-rifle to hit through the front of Ion Armor for 39 damage (enough to kill some soldiers) or for a Sonic Cannon to hit through the front of Magnetic Ion Armor for 92 damage (enough to kill almost any soldier) -- if you have weapons hitting for 0% - 200% power, which is the default. Turning your front to the enemy isn't fail-safe but it is extremely effective.
#6
I had no idea a HE shell guarantees a kill on a Reaper. That's a good method then. 2x2 units are generally weak to explosives even if they don't have a weakness to HE-type damage because they can get hit by the blast 4 times, one for each square they take up.
Why kill stunned Mutons/Lobstermen? So they don't get up later. Useful for long missions, especially if they get long exactly because you are having to stun every enemy to kill it.
Lobstermen sure are weak to melee, but you don't get Vibroblades without recovering one for research. Sometimes (often, really) you'll end up fighting Lobstermen before you have sonic weapons or vibroblades.
#7
On multiple occasions I've actually had brainsuckers attack my soldiers during reactions. This isn't some fluke that rarely happens. I probably see it more than most people because I have a habit of running a soldier to point-blank range with the Marsec M-4000 Machinegun. It's generally a really good strategy for fighting most aliens but it can be good to keep a square between you and a brainsucker.
#8
Already addressed by Yrizoud (Reply #11) -- You don't have to check it incessantly. I usually check it fairly frantically (multiple times per day) for the first few days until I get myself a catch. That graph work is less work than restarting at the end of the month because you didn't shoot down any alien craft and eight nations have already reduced funding and threatened to withdraw.
#9 -empty-
#10 Actually I don't recommend nuking large rooms first usually. Overall it's just best to learn all the spawn points so you can pick good striking points. Some people like to leave the majority of the ship intact, or might want to save Elerium (either in the ship or in production of blaster bombs), or even might just want to not fit very many blaster launchers in the squad. When you're being picky about which room you'll nuke, the navigation room is a good choice for maximum damage.
