From Scripture, what are the signs of demonic presence? From scripture, what are the signs/manifestations of demonic presence? 

Can scripture be used to bring out and away the demonic presence?

What warning signs should be looked for as far as the various stages and progression of the  demonic presence?
I don't know if this type of answer is allowed, but my reason for posting is to try to help you. It's what I have seen in real life.

My younger brother's best friend, who lives down the road from us became demon possessed, he comes from a really good family, they are christians, he's a really nice kid, hard working, always helping out his family, didn't really get involved with anything bad. 

My brother who hangs out with them often started noticing weird things about him, as did his family. I should note that later we found out from him he became possessed much earlier, but it did not show right away. As soon as he tried to get rid of it, by repenting of everything he could possibly think of, the problems started, and he was arrested and in a mental institution under heavy sedatives within a week.

He seemed to switch personalities randomly while talking, one minute he's his normal self, and the next he says weird things which contradict the bible or what he normally thinks, then he will switch back and continue being himself. My brother said he would start to act like a different personality. This got progressively worse, he started not sleeping and barely ate anything, he was skinny to begin with and lost 15 pounds within a short period of time, he also became violent towards his family members whereas before he was a really gentle kid, for example he threw his younger sister down on the floor and yelled for no reason, they started to be afraid of him. He would also come home and report how something is trying to kill him while he's driving, by making him go really fast and weave across the road... when he visited a church an hour away with our churches youth he stayed after and started fighting someone yelling obscenities (this is so out of character for this guy) and to top it off he called the cops on himself. He also, jumped out of the car and ran away, the cops later found him in just his boxers and nothing else on roaming around and brought him home.  The things he did where basically self destructive and socially embarrassing. 

When they prayed together with his family in the evening as normal, he would obey his parents and kneel down, but he would not actually pray himself. He also, didn't want to or couldn't say the word Jesus. His mother was really getting scared and desperate at this point and she knew of a man from her former country that could get rid of demons so she went to another room shut the door and called this guy, but her son not even knowing that she was calling and being with the family in the living room (they have a large house)  started screaming NO! NO! NO!, so the guy on the phone said let me speak to him. The kid took the phone and the man said Do you know who I am? The kid said yes you are a man of God... anyway his mom bought this man a ticket to the states, we live in Washington but the man flew in to california to meet with some local church leaders there to pray together prior to meeting her son... On the way to California, they stopped at a friends house for the night, in the evening he grabbed a huge kitchen knife and tried to stab his father, he was violent towards him when they were at home too,.... basically he threatened to kill everyone I guess he was trying hard to avoid getting to california, so they obviously called 911... the police came but wouldn't enter the house.  So everyone was stuck with a crazy guy inside and a whole squad of armed police outside... they started praying and coaxing and finally were able to get him to put down the knife.... police came in and arrested him and took him to the mental hospital so he didn't make it to california.... I should note that by this time our church was praying and our church leaders were fasting for him and everyone knew about it. At the hospital they ran a lot of tests but could find nothing wrong with him... however he was kept under a large dose of really bad sedatives so mostly he slept the whole time. When he got a chance to go up before the judge to see if he could be let out, he acted normally enough, but when he spoke with the judge he called him a satan so he got sent back to the mental hospital. Finally, the men from california came out and prayed for him for a long time to expel the demon and the demon left him... he was slowly weaned off the sedatives but still required a small amount regularly because he became easily excitable... he would talk a lot and fast and got overly interested in the bible continually annoying everyone and asking a ton of questions... so they took him to a rehab facility for addicts, there where people there who had experience with this type of thing... he lived there for I think a week they shaved his head.... told him to take off a little woven bracelet he had on his wrist which he bought in Mexico and prayed a lot for him, now he's back to normal completely. 

How did he become possessed? A demon cannot take possession of just anyone they wish to... you have to have some type of door open for it to be able to do so. In this guy's case he confessed to becoming interested in the illuminati, it started innocently enough with him researching it online, it was later discovered he had collected every single illuminati shirt and had them hidden in his room, and became more and more obsessed with finding more information out about it... finally on a school trip he visited a university here in washington (he was trying to pick where he was going to school), and met someone at the school orientation or at the campus who he called "the doctor", it was really a chiropractor, who he told us, told him he can become rich and powerful really quickly without going through all the trouble of school or with doing very little school? im not sure, he met with this guy privately, and after that he became possessed and would talk about how great this doctor was to anyone who would listen.  He was really infatuated with this guy and even tried to get my brother to go "visit him" when my brother was in Seattle, which happily my brother wasn't able to do because he was busy. Moral of story don't get involved in the illuminati and don't wear any mexican woven bracelets, don't get involved with anything from the occult or horoscopes, and fortune telling, because these will open the door for satanic entities.

The only other thing I've heard of is a man who was demon possessed for 15 years, and he was kept chained to the living room floor, was aggressive to everyone but would allow his wife to bring him food and clean up after him.... I don't know what happened but he was rid of his possession and went back to a normal life after all those years.... the poor wife though stuck by her crazy husband through all that time.

If you want to see examples of demon possessed or dedicated followers you can look at celebrities and world leaders.... some of them will even put things in their music or say things in interviews that they made a contract. One example of someone trying to back out of their contract is Britney Spears, Britney's not crazy, but many people think they can sign a contract get what they want, and then back out whenever they feel like.... and that's not really the case.