The key to heal people and do other miracles, is to have faith in God regarding prayer answers etc. For instance this faith: God will do the miracle one pray for, if there is no reason to not do it. Faith is one of the big keys in the bible, so also when it comes to doing wonders / miracles.
If one are a christian, and belive that God basically will heal the person one are laying hands on, then one will start to see people getting healed and set free, when one do laying on of hands and pray for people,.. as long as one’s faith is strong enough to compensate for the others lack of faith.
Maybe the first one will not get healed, but if your faith is strong enough to that you can do healings, you will sooner or later see people getting healed by this faith.
«So Jesus answered and said to them, “Have faith in God. For assuredly, I say to you, whoever says to this mountain, ‘Be removed and be cast into the sea,’ and does not doubt in his heart, but believes that those things he says will be done, he will have whatever he says. Therefore I say to you, whatever things you ask when you pray, believe that you receive them, and you will have them.» Mark 11.22-24
The bible-verses above, as about getting something oneself by faith,.. and when one are praying for someone, it will be a combination of faith of the persons praying, and the faith of the person being prayed for (which faith one have to that God will help if that’s the best all in all),.. exept if the person being prayed for, has the strongest faith (then the prayer-result, will probably follow his/her faith instead).
«And He said to them, “Go into all the world and preach the gospel to every creature. He who believes and is baptized will be saved; but he who does not believe will be condemned. And these signs will follow those who believe: In My name they will cast out demons; they will speak with new tongues; they will take up serpents; and if they drink anything deadly, it will by no means hurt them; they will lay hands on the sick, and they will recover.”» Jesus quoted, in Mark 16.15-18
After one have prayed for someone with laying on of hands, one can ask if they can check if it has become better. If not, one can e.g pray one or two times more.
Not all healings come instantly, but sometimes a healing comes more gradually (e.g over some minutes, hours, or some days).
If one cast out a demon, then the demon can start to manifest in the person, but if it’s faith for it, one cast out demons instantly (without any manifestations).
Reccomend to also read to article: «About healings by prayers, laying on of hands, etc»