In Siege, there are two sides to each match, Attackers and Defenders, this will focus on how to properly set up a defense and some tips on how to defend a position. The first step in the defense process is making sure you have put up all of your reinforcements. Each operator gets two reinforcements that they can place on any soft wall or hatch they see fit. The most important places to reinforce are the walls that are on the exterior of each objective. If you are playing Hostage or Secure area, there will only be one room that needs to be secure, but if you are playing bomb, then there will be two rooms that will need to be secured. If you can manage to get the exterior walls of the objective rooms reinforced, you make the attacking team either breach through those walls which will give away their position, or you force them to come through the doorways that lead into the objective. The next step is to be aware of where the hatches are on each map. If there is a hatch that is directly above the objective room, that is a high priority hatch that needs to be reinforced so the attacking team does not just get an easy shot on you from above.
Once you have gotten those reinforcements up, the only step left is placing all of your equipment down that will also slow the attacking team down. First, if you have an operator with barbed wire, you will want to place that in doorways or in places where you know the attacking team will have to go through. This slows them down and forces them to either walk through it, which makes plenty of noise, or destroy it by melee, this will also make noise and leaves them vulnerable to an ambush. Deployable shields can also be placed in doorways which force attackers to jump over it in order to get past it. Depending on which operators you have on your team, you can place a trap behind the shield to take out the first attacker that jumps over the shield. If you are playing bomb, most likely the bombs will be in rooms next to each other. If you have an impact grenade, you can throw it at the wall that splits the bomb rooms and by doing that, you will link the two rooms into one. This will allow defending players to rotate between the two rooms without having to go in the hallways and risk running into an attacker. This is one of the most underrated moves in Siege, many people will not do that and force themselves to run all the way around to find an attacker in the other room.
This should all be done within the “Prep Phase” which is the time the defending team gets to set up their defense and the attacking team gets to use drones to find the objective and identify the defending operators. After the Prep Phase, you need to figure out which operators are going to roam (if any) and then which ones are going to be in the objective as a support operator. If you have a hatch right above the objective, I would recommend sending one operator upstairs to defend that hatch or die trying. It is crucial that you have at least one player in each objective if there are multiple, and always have someone watching each way into the sites. Also, checking the cameras is something that a lot of Siege players ignore, they can be the most helpful tool you have. By checking the cameras, you can see who is on the attacking team and get an idea of where they will be coming. By doing this, you can send someone out to intercept them and pick one or more of them off without them expecting a thing. If you are playing bomb, one operator will have the “Defuser”, this is the device that the attacking team has to plant near a bomb in order to complete the objective. If you kill the player holding it, they will drop it where they get killed, stay there because there will be someone else who will have to come and get it. At that point, forget about the bomb rooms because without the Defuser, they have no way to win without killing everyone. Above all else, communicate with your teammates because even the smallest amount of information can be the reason why you are able to win a round.