One of the most beautiful questions of NS.
lets see...
1) Blocking. Hide beside a door somewhere. When the fade blinks in, move so you're standing in the doorway. Retreating fades tend to go the same way they came, so he'll likely be coming back at you. Depending on his health, he might even attack you. But if you get in his way, your body will completely stop his blink, and he'll either have to spend the extra time to kill you, or to get around you, or to turn away. That extra time means extra damage into him, when he's already hurt (retreating). A good method.
2) Catching a fade on a retreat. Similar to blocking. Hide somewhere, but when the fade passes you by, just wait. Let other marines do damage to him. Find a nice corner, so you can see down two hallways. Start shooting him as soon as you see him (having Motion Tracking helps you track him on the map and be ready). Since a fade would only be coming back like this (well, not always, but usually) when he's hurt, you already have a much better chance at winning the battle. Shoot right away; often the fade will panic, and run past you. This is where the corner bit comes in; you shoot at him while he comes down the hall, but you can keep shooting him while he runs down the next one. A good tactic, and be sure to whip out the pistol for that last quick barrage.
3) Tightly packed mines. Mines do need to be spaced out a certain amount, but nothing's stopping you from putting them exactly that distance away from each other. Try putting them on the walls that fades might blink into, perhaps one of the exits from Marine Start. Then, camp the other exit; when he comes in, block him, so he hopefully goes out the other exit. Bam bam bam bam, 500 damage in mines. Hopefully.
4) Shotguns tend to be better than HMGs against fades, whereas HMGs are better at killing everything else. Reason being, is that hmgs are LOUD, and do their damage over time. A good fade will hear the HMG and immediately play a bit more defensively. Shotguns on the other hand, are not heard until the fade is right up against it, and his health drops instantly. This is just my opinion though.
5) Aim for the exit. Fades and lerks are so fast that once they decide to retreat, they tend to make it out quickly. As soon as you see a fade turn, aim at his most likely exit and just rip it. This will have a much higher chance of actually hitting the fade then trying to track him when he's blinking at full speed.
6) Shoot him some mo'. Remember that damage 3 is pretty and all, but its only +30%; another LMG is + 100%. An HMG deals twice the damage of the LMG for 2.5* as long (which will never all be spent on a fade), but two LMGs together can do just as much. More marines, more bullets. And good fades play differently depending on how many bullets they're up against, so if you have 4 marines but 3 of you hide, the fade will see the loner marine and be way off guard. Let him come in, try to block his exits, and unload.