Identifying Demonic Activity and Dealing with it:
Most people have experienced some awareness of the demonic around them since becoming born again. You were renewed by the blood of Jesus and sealed with The Spirit of Truth inside,.... so yes, you now are able to know about this activity whereas before you were blind to it.
Demonic activity that you can encounter at times can range from something black moving nearby you out of the corner of your eye when shown by the discerning of spirits, to the manipulation of events around you, normally ones that are meant to come against you somehow. You can also be shown people who are filled with these things at times, when they start to cuss at you in stores and such. This normally only happens in response to the amount of holiness and closeness to GOD you are walking in.
So where could we encounter these things at times? How about in church?
Oh yea,.... Christians who are not all that close to GOD, who only associate themselves with GOD on Sundays, and mingle and frolic with the world the rest of the week, can drag all sorts of these things in with them on Sunday. They tend to attach themselves to folks who are not abiding by what scripture says about separating themselves.
Is your worship dead? Having a hard time in prayer throughout service? Can't seem to connect with GOD? Most likely these things are affecting people in the spiritual realm. Really though, you will begin to just assume they are in the service once you begin to realize how many folks are walking in the flesh as Christians.
So,... what can be done?
Whelp,.... let's look at something Jesus did and educate ourselves,....
Luk 8:28 And when he saw Jesus, he cried out, and fell down before him, and with a loud voice said, What have I to do with thee, Jesus, thou Son of the Most High God? I beseech thee, torment me not.
Luk 8:29 For he commanded the unclean spirit to come out from the man. For oftentimes it had seized him: and he was kept under guard, and bound with chains and fetters; and breaking the bands asunder, he was driven of the devil into the deserts.
Luk 8:30 And Jesus asked him, What is thy name? And he said, Legion; for many devils were entered into him.
Luk 8:31 And they entreated him that he would not command them to depart into the abyss.
Did you catch that last part? It wasn't just a deliverance of these things out of the man by Jesus, He was able to command them out of this world and into the abyss below, and these things knew it and worshipped Jesus in their own way to not do it. This was an authority that Jesus had down here which is normally not noticed by any of us in scripture.
Well guess what? This authority passed onto us also, most of us just don't know it.
So how does this work? Well let's look at scripture again,...
Mat 16:19 I will give unto thee the keys of the kingdom of heaven: and whatsoever thou shalt bind on earth shall be bound in heaven: and whatsoever thou shalt loose on earth shall be loosed in heaven.
This is sort of a generalized portion of scripture by Jesus. It can fit many types of situations for us because it is not specific. So by faith we apply this to our situation when we suspect that demonic activity can be happening around us.
Here's how I apply this:
I'll say "Father, I bind any evil spirits, principalities, and powers trying to affect us and this place. I bind them and cast them down, into the abyss, into the pit, never to be brought back up here to affect anyone or anything ever again, Father in the name of Jesus."
And I will immediately follow up this command by praying in the spirit to GOD, and myself.
I normally will always say this quietly to GOD and myself right after I get to church. If I think I need to say this again before worship starts, then I will do it again. I want our service to be connected with GOD with nothing in the way hindering it.
This was the very first tool that GOD showed me to use in situations, and I've used it plenty over the years. If I see something black out of the corner of my eye that I think The Holy Spirit showed me, I will say this same prayer but change the wording a bit just to make it more personal to me at that moment. I've never had it not work, and because it works, I don't have evil spirits messing with me anymore. Satan doesn't want to keep losing his forces this way around me.
If people are somewhat unsure faith-wise in doing this, then ask Jesus for the faith in it. We live by the faith OF The Son of GOD, so He is more than happy to give that to you. That's what He did for me.
EDIT: I updated the binding/loosing instruction and highlighted it. It is much more effective if you identify where you want them to go, like Jesus did in the supplied scripture example.