Best locations for Symmetra's Teleporter? [closed]

There are too many good positions to actually list as an answer.

The general idea you want to follow is - place the Portal just behind the objective, on your side of the map. For instance on Hollywood, you can place the Portal just next to the Huge doorway right before you reach the A point on Defending.
Generally enemies wouldn't be going that deep before they've captured the point, and its close enough for you to use. Another good position on this map is the bushes behind the A point, next to the elevator, which later become the enemy's spawn.

It's difficult to give any specifics about this, because it's going to vary based on enemy team composition and how far pushed they are.

I like to place teleporters in areas that give my team a shorter run back, but don't compromise the safety of the teleporter itself (it's worthless if it is destroyed, after all).

To identify the best places you'll need to look at the enemy team. If the enemy team has flankers, you don't want to place the Teleporter too far away from any defenses. You also want to minimize the lines of sight an enemy has on your teleporter, because if they can't see they're much less likely to destroy it.

Typically I place my teleporter near where my team is currently defending, but as hidden as possible (either with props or in a hallway). It's also a nice idea to mention where exactly you put it in team chat (not match chat) so your teammates are less disoriented when taking it.

As others have stated, a comprehensive list here would be too much. Here's some general advice. I'm also trying to address some topics that directly relate to good teleporter placement. If you need a short answer, check the bold text below.

First, be aware that when placing the teleporter, the exit is facing towards you. So if you look into a corner, players will exit facing away from the corner. Try not to let players exit facing a barrier.

Think about the line of sight the other team will have as they approach the area where you want to place your teleporter. If you're on defense, you want to consider which positions around you have the least amount of enemy activity in addition to visiblity. This is often near the objective, but some maps may provide opportunities closer to the attackers, based on player skill and behavior. If the enemy tends to charge down the main lane and shows no sign of flanking activity, you will have a lot of safe areas. If you're on the attack, you need to find a position not easily seen, that is closer to the objective but not so close that defenders will regularly encounter it. On most maps there is a single choke point, such as a wall with an opening, just before the objective. Before this choke point would be a good area to look for a teleporter setup.

Your teleporter only has six charges, so you don't have to think about it as a permanant fixture that you need to defend. If you spend too much time keeping it safe, you won't be able to assist the team with support fire. (The secondary charge shot of her weapon is fantastic, but not relevant to this question.) Also, be careful about putting turrets next to your teleporter. This does help defend the teleporter, but it also increases the visibility of its location. Some players will call out the presence of turrets and other players may come to help clear them out, and spot the teleporter.

Unfortunately, as of this writing, players you kill will be able to see your teleporter HUD indicator on the kill-cam. This will give them a clue to the location.

Finally, enemy players are dangerous creatures that may attack at any time. If they see your teleporter in one position and destroy it, they will often remember that and check to see if you rebuild it there. Once they're aware of what you're doing, you'll need to switch up your locations, if you have time to build a second teleporter.

If setup properly, you will save members of your team valuable time, and let them get back into the fight quickly. In the event you die and respawn by your teleporter, consider whether or not it would be better for you to walk back and let a more direct-combat oriented character use one of your charges instead.

In addition to points mentioned in other answers, such as

• place it out of line of sight
• place it near enough to the objective to be useful but not so near that the enemies are likely to find it
• place it so that your allies come out facing in a reasonable direction

I'd like to add an additional point:

• place it somewhere where you can see anyone coming out of it before they reach the action

Then, pay attention for any teammates that die. Once they do, turn to your teleporter, and hit them with a new shield once they pop out.