Attacking is easily the hardest part of playing Rainbow Six Siege, you are going into a building that has been fortified and you may not know where you are going to be shot from. Each attacker does get to drone out the objective and scout out the defense during the Prep Phase, but that does not always give you the information you need in order to have a confident attack. It is very common for defenders to not fully set up their defense, especially their trap operators until the Prep Phase is complete and the attackers are no longer on their drones. After a recent update, there was a patch that allowed the attackers to stay on their drones after the Prep Phase has ended. This was a huge step for attackers in the way that they would not lose their first drone after the Prep Phase, and that they could continue to drive around and be able to spot traps and possible ways in that would avoid the majority of the traps. For most attacking teams, having at least one hard breacher is essential to gain a win. This meaning either having a Thermite or Hibana on your team can be the reason why your attacking strategy works. The best way to operate this form of attack is to assign one other player on your team to escort and cover the hard breacher while they attempt to breach into the objective. That is fundamental on all 3 possible objectives (Bomb, Hostage, and Secure Area). If the defending team has a roaming operator like a Caviera or a Vigil, then you would also have one or two of your teammates assigned to hunting down that roamer and eliminating them before you continue your attack to the objective.
Using your second drone is a tactic that many beginning players do not realize. Using that second drone to guide the rest of your attacking team safely onward is a big step in the attacking process. The player operating the drone can alert the rest of their team if they find a defender that is away from the objective and is waiting to ambush someone as they approach. Drones are very distracting and as an attacker, you must use that to your advantage. One thing that you need to make sure of, is that you do not have your entire team approaching from the same direction, this would allow the defending team the ability to hold multiple angles on the same area. This would catch your team in a crossfire, which is the last thing you want as an attacker. What you as an attacker should be doing, is having your team approach from different angles and areas. This would allow your team the ability to catch the defense in a crossfire or to catch a defender trying to move and reposition themselves in a better spot. As always, communicating what you see and where the defenders are going is a huge step in making sure that your team has the best chance to control the round. In the scenario that you are playing the bomb game mode, there is a slightly different way to complete your mission. If you have an attacker that has a smoke grenade, which there are plenty of, or having a Capitao (Crossbow smoke arrow). If you can get a smoke grenade deployed inside the objective sight, you have given cover to the player who is going to plant the defuser, which is what the defending team is trying to prevent you from doing. If you can manage to get the plant off, you have changed your role from an attacker to a defender. You no longer need to attack the opposing team, rather you will then defend the defuser and put the other team into attack mode.
The other important part of attacking is knowing where you are on the map and where the cameras are. If you have that knowledge, you can either find a way to the objective that has the least number of cameras surveying it or you can destroy those cameras before the defending team has the chance to use them. Having the element of surprise is what you are banking on. If the defending team knows where you are and where you are going, you will have a hard time breaking through the defenses without being flanked or risking a firefight that the defenders’ have the upper hand in. Finally, knowing the defending operators is a huge factor. Knowing which operators the defending team has selected can give you a hint on where they will be and how they will use their ability. For example, if you see the opposing team has a Kapkan or a Frost, you will know that jumping through windows or doorways will be a high-risk mission. This is because those two operators are the ones who place their traps specifically in these positions to ensure that they have at least a warning if you chose to come in from that location. If you can notice that and destroy those traps before anyone hits them, you can then turn the element of surprise on them and catch the defending team off guard. Communicate with your team and relay information when you have it, that can easily be the reason why you have a 3-1 advantage of operators rather than the other way around.