Basics
Portal Basics
Before thoughtlessly (dangerously?) stepping foot into your first portal, take time to learn the basics of Portal play. Obviously, this isn't an every-day sort of first person game.
Rules of the Portal Gun
Blue to Orange, Orange to Blue
This is the basic premise of the portal: go in through the blue portal and you'll come out through the orange portal. Or reverse! Go in through the orange portal and you'll come out through the blue portal. This rule never fails, and the portal gun never gets more complicated than that.
Portal Surfaces
Using the portal gun, you can create portals pretty much anywhere you want...provided there's a surface to stick to. Certain textures—generally dark-colored walls—will not take portals. As well, you cannot stick a portal to a wall that doesn't have room for the full size of a portal. There's no limit to how many times you can fire the portal gun, but don't be surprised if you're unable to create a portal on certain walls. As you get deeper into the game, the surfaces that reject portals become more numerous.
Can You Shoot Through Stuff?
No! At least generally. Though some surfaces, like glass, will not take portals, you can not shoot through them to hit portal-able walls behind them. As well, you cannot shoot portals through particle fields (those barriers found in front of every chamber's exit). And you cannot shoot portals through other portals.
You can, however, shoot portals through mesh grating. Go figure.
Incandescent Particle Fields
Incandescent particle fields are those pseudo walls that are in front of every testchamber exit. You can walk through these electronic fields without a problem, but you cannot carry objects through them. And like we said earlier, you cannot shoot portals through the particle fields. More importantly, portals you've created will actually disappear every time you pass through an incandescent particle field. Just think of these particle fields as big, intangible reset buttons for your portal gun...and your items...and your hopes.
Momentum Jumps
Momentum jumps are one of the dopest and illest aspects of Portal play. The basic idea is that if you build up momentum before heading into a portal, you'll carry that momentum—that forward motion—as you exit the other end of the portal. Generally, the best way to build momentum leading into a portal is to drop down into it. Fire a portal on a ground level far below you, then jump from a higher level, diving into the portal. You'll build up speed during the fall which will continue to propel you out of the exit portal.
Generally, momentum jumps are used to sort of catapult yourself over chasm. Lay down an orange portal on a vertical wall overlooking a chasm and drop the blue entry portal on a low level ground. Take a massive dive into the blue portal and you should shoot out of the orange portal, flinging over the chasm. Told you it was ill.
ENEMIES!
Alright, so Portal's not a typical first person game, and generally your only adversary is the challenge of the puzzles. However, there are some potentially dangerous "enemies" to watch out for.
High Energy Pellets
These bouncing energy balls are generally part of a testchamber's puzzle, and while they may seem harmless they are actually not. Getting hit by an energy pellet means instant death, so be careful in rooms where they're bouncing. Generally, you can crouch underneath the energy balls to avoid their sting. Also, if you're holding a weighted storage cube in your hands, you can use the cube to deflect the energy pellets.
Turret Buddies
We call these little turrets buddies because they're so adorable, but don't take them lightly. If a turret locks onto you with its laser sight, it'll drill you into submission with machinegun fire. The turret buddy's weakness? They tip over so easy! Portal warp behind a turret buddy and you can simply pick it up and toss it on its side. As well, you can create portals over the top of turrets and drop objects (like weighted storage cubes) through the portal and onto the heads of the turret buddies.
Allies
Weighted Companion Cubes
No words are necessary.