I made this early February and forgot I didn't post it here lol.
This is just some general tips to get better at spy. Reading this won't automatically make you better, the biggest thing is practice!
When disguising as spy. I won't lie. The disguise is useless. Everyone shoots everyone. You won't do much 'pretending' to be the other team. Don't spend too much time near someone on the enemy team while wearing a disguise. They will shoot you.
Stay away from pyros. Some retarded shit face at valve, decided that FF off is a good thing. So you can shoot everyone on your team, and only kill spies! Fantastic, especially when you can just burn everyone and only the spies will set on fire. There should be an FF on server option to make it fair. But there isn't, so just stay the fuck away from pyros.
Choosing who to disguise as. Don't disguise as spy. People shoot spies whatever team they are on. Its stupid. Also if you disguise as medic people can see that there isn't an ubercharge % under your name. Bad idea. As scout you move slower than scout so it can be a dead giveaway. Heavy and soldier slow you down too much for my liking. So generally I disguise as Pyro and Demo to get to their base and sniper/engi when I am in the base. And disguise as soon as you leave your base. This way if there is a sentry you don't know about it won't shoot you.
Getting to the enemy base. People walking the wrong way are very suspicious. Try and find a way where you won't meet many people. Use you cloak to get around crowded areas. Make sure you don't walk into anyone. Keep an eye out if you start to run low and find a safe spot to hide. If you are cloaked you can still be set on fire, and try not to get in the middle of firefights. Also when cloaking after coming out of water you will be dripping, so watch out.
Never use a teleport. Unless you plan on waiting until the trail goes out you will have a glowing trail showing everyone where you are. This doesn't matter anymore. The trail disappears when you disguise. Unless you are feeling kind and still want to let others use the tele.
Taking out sentries. Unguarded sentries. These are relatively easy. Just place the sapper on the sentry. If you think the engineer is coming back then get out your revolver and shoot at the sentry to quicken its demise. Remember to disguise again afterwards.
If there is an engineer near the sentry then there are a few things that can happen.
1. You sap it and the engineer just keeps hitting the sentry with his wrench. This is good for you. You can just keep sapping it. It will eventually die and you can take him with your revolver.
2. You sap it and he gets out his shotgun. Go invisible and try and get away. Use open spaces and try to go in random directions. Hopefully he will be more focused on you and leave his sentry. If not, just keep trying.
3. You sap it and he goes around it with his wrench fixing it and trying to hit you. You should be able to outmanoeuvre him and keep sapping. If you get low on health just retreat.
Those are the main three I can think of. If there are other enemies near you its pretty hard as the engi can repair and others can kill you.
A good thing for you is when the engineer is standing behind the sentry gun hitting it. Get behind the engineer. Get your knife out end backstab him. You have to get the timing just right. After backstabbing him walk forward press 2 and just keep clicking. You should be able to get the sentry and any other buildings in the vicinity. Watch out for pulling out the sapper too fast. If you pull it out before the engi is dead then you will most likely just die.
Also remember your revolver. If someone starts shooting you just get out your revolver. Its one of the best weapons in the game. You should be able to take most people in a 1 on 1, especially if you get a crit. Your revolver is also good for destruction. If you are out of range to sap something then just shoot it with the revolver. Good examples of this are on ctf_well. Hiding in the enemy base you can destroy buildings outside their base from their battlements and also tele entrances etc outside their spawn from the top level of their base. Also good in their intel room taking out sentries from the other side of the room.
I might add more another time. And I did it quite fast so some bits may not make sense. But meh, hope its useful.
This is just some general tips to get better at spy. Reading this won't automatically make you better, the biggest thing is practice!
When disguising as spy. I won't lie. The disguise is useless. Everyone shoots everyone. You won't do much 'pretending' to be the other team. Don't spend too much time near someone on the enemy team while wearing a disguise. They will shoot you.
Stay away from pyros. Some retarded shit face at valve, decided that FF off is a good thing. So you can shoot everyone on your team, and only kill spies! Fantastic, especially when you can just burn everyone and only the spies will set on fire. There should be an FF on server option to make it fair. But there isn't, so just stay the fuck away from pyros.
Choosing who to disguise as. Don't disguise as spy. People shoot spies whatever team they are on. Its stupid. Also if you disguise as medic people can see that there isn't an ubercharge % under your name. Bad idea. As scout you move slower than scout so it can be a dead giveaway. Heavy and soldier slow you down too much for my liking. So generally I disguise as Pyro and Demo to get to their base and sniper/engi when I am in the base. And disguise as soon as you leave your base. This way if there is a sentry you don't know about it won't shoot you.
Getting to the enemy base. People walking the wrong way are very suspicious. Try and find a way where you won't meet many people. Use you cloak to get around crowded areas. Make sure you don't walk into anyone. Keep an eye out if you start to run low and find a safe spot to hide. If you are cloaked you can still be set on fire, and try not to get in the middle of firefights. Also when cloaking after coming out of water you will be dripping, so watch out.
Never use a teleport. Unless you plan on waiting until the trail goes out you will have a glowing trail showing everyone where you are. This doesn't matter anymore. The trail disappears when you disguise. Unless you are feeling kind and still want to let others use the tele.
Taking out sentries. Unguarded sentries. These are relatively easy. Just place the sapper on the sentry. If you think the engineer is coming back then get out your revolver and shoot at the sentry to quicken its demise. Remember to disguise again afterwards.
If there is an engineer near the sentry then there are a few things that can happen.
1. You sap it and the engineer just keeps hitting the sentry with his wrench. This is good for you. You can just keep sapping it. It will eventually die and you can take him with your revolver.
2. You sap it and he gets out his shotgun. Go invisible and try and get away. Use open spaces and try to go in random directions. Hopefully he will be more focused on you and leave his sentry. If not, just keep trying.
3. You sap it and he goes around it with his wrench fixing it and trying to hit you. You should be able to outmanoeuvre him and keep sapping. If you get low on health just retreat.
Those are the main three I can think of. If there are other enemies near you its pretty hard as the engi can repair and others can kill you.
A good thing for you is when the engineer is standing behind the sentry gun hitting it. Get behind the engineer. Get your knife out end backstab him. You have to get the timing just right. After backstabbing him walk forward press 2 and just keep clicking. You should be able to get the sentry and any other buildings in the vicinity. Watch out for pulling out the sapper too fast. If you pull it out before the engi is dead then you will most likely just die.
Also remember your revolver. If someone starts shooting you just get out your revolver. Its one of the best weapons in the game. You should be able to take most people in a 1 on 1, especially if you get a crit. Your revolver is also good for destruction. If you are out of range to sap something then just shoot it with the revolver. Good examples of this are on ctf_well. Hiding in the enemy base you can destroy buildings outside their base from their battlements and also tele entrances etc outside their spawn from the top level of their base. Also good in their intel room taking out sentries from the other side of the room.
I might add more another time. And I did it quite fast so some bits may not make sense. But meh, hope its useful.