Five Steps to Playing Well Edit
Part 1: Inflitrate the enemyEdit
The moment the round starts, immediately activate your cloak and head towards the front lines. Depending on the map, your approach towards the front lines may differ. On ctf maps, try to use the less popular routes (generally the lower sewer routes).
Part 2: Plan Edit
Once you have made it into the enemy territory, start choosing your targets. Try to find lone or distracted enemies to maximize your survival rate. If you're fortunate, your teammates will be providing the necessary distractions (ubers and autoguns make excellent ones), allowing you to get in a couple free kills without the enemy knowing of your presence until it is too late.
Part 3: Retreat Edit
After every strike, make sure you either recloak and get out of the area, or rejoin your team to get healed. The enemy and your victim will likely go looking for you, so some form of escape is necessary. If you rejoin your team, add some shots of your own with your revolver. It's an underrated weapon. Knowing where to hide and when to hide may be the difference between staying alive and meeting your demise. After things die down a bit, repostion yourself and select another target. However, no matter how well you evade detection, there is always a chance you will be randomly found.
Part 4: Watch and Learn Edit
Being observant is one attribute that the Infiltrator needs in order to be sucessful. as you'll never know what could be heading your way. Not only must you keep a lookout for yourself but your team as well. On your way towards your destination you may come across a Detonator setting up a sticky trap which can be a nasty suprise for your teammates, not to mention yourself. If he is alone or his teammates wont be able to reach him in time engage him. Once he is dead cloak and get out of the area. Another situation that requires observation is chokepoint standoffs.
Part 5: Out of Sight, Out of MindEdit
Stay out of sight and out of the enemy's line of fire. It is important to keep yourself as hidden as possible so that way you can come into any situation without being noticed, allowing you to set up for a kill. Try to avoid jumping, as many good players will hear you and will know of your presence. Also, note that passive invisibility lets you stand behind enemies, uncloaked, without them being able to see you.
Dealing with enemies Edit
Dealing with Constructors and their autoguns can go one of two ways: One, you manage to slip behind the Constructor and give them a nice tap on the back with your knife and destroy their autogun, allowing your team to move in. Two, you come across a Constructor who has dug himself into a spot that is near impossible to take out alone. That doesn't mean you can't kill him anyways. Another teammate distracting him from a different angle is a perfect oppurtunity to destroy his autogun. If you have no help, try uncloaking nearby and lure him away. Then, shoot him down with your revolver. Try to back away and take them on over a long range where their shotgun is less effective.
Occasionally you'll come across the situation of counter espionage, which means tracking down and killing enemy Infiltrators. Often check the killboard in the upper right corner to see if anyone on your team has been killed by an Infiltrator. Sometimes you may see a fireball randomnly floating in midair which means an enemy spy has caught aflame. Pursue and shoot them down, theres nothing worse than another Infiltrator taking out your defenses and stealing your intel while you're away.
If you get stuck behind the enemy frontline, but most of their team are firing/spychecking, a good tactic is to uncloak, fire all six bullets in your revolver then recloak and move away. This will often distract some of the other team, while also dealing some damage (6 bullets can do up to about 160), and during the time that they have been drawn away from said front line, you can move in and destroy any autoguns or low-health players. One thing to remember when using this tactic is that any time you get hit the enemy can track you; therefore it is necessary to avoid all damage, especially fire, else returning recloaked and destroying defences will be nearly impossible.
One last thing that must be remembered is that if your team already has about two Infiltrators, your team does not need anymore, as a third infiltrator does the team very little. The lack of real fire power and defense can really destroy your team's chances of victory.
Unlike the TF2 Spy, who can move while initiating a stab, the Infiltrator is unable to move for approximately 2 seconds while stabbing unless moved by an outside force (explosion, bullet, Q/C sword, airblast). What this means is that in order to get a successful hit with the knife, you must time your stabs in relation to how fast your target is moving. Each target ranges in difficulty, with Runners typically being the hardest to stab and Overweights the easiest. Luckily, it does not take long to learn the timing to stabs.
Many Infiltrators never use their revolver and because of this, get killed constantly. The Revolver is not a sidearm, it is your primary weapon. Targets who are out of your range should be dealt with the Revolver first hand, instead of stalking them cloaked and trying to go for a stab. The Revolver is also favored during situations when you are being chased down by the enemy such as Firebugs or Runners. Use it as a deterrent as either your pursuer will back off or die hunting you down. Each round from the Revolver does 25 damage so don't feel shy to bust it out and lay down some suppression fire. When reloading, cloak. There's no reason to stay visible while your gun's empty.
If you can't kill constructor and his Autogun, try to jump and stab. The time it takes to land is about 0.7 seconds, so when you land, you will stab. Also, this strategy is good, because enemy probably won't gonna move out of the way.