I have some really good friends who claim that they are Christians but I know for a fact that they aren't saved and I'm not exactly sure how to talk to them about Christ and getting saved. I also hear some of them who claim to be Christians say that they are glad that their parents don't go to church because then they wouldn't be able to sleep in on Sundays. I have brought a couple of them to my church but they acted like they didn't like it. How should I convince them that they should believe in Christ?
My second question is this: I have a friend who always talks about Christ and how he has changed her life. But I know that she hasn't been saved. Do you have to be saved go to heaven?
Having an attitude of trying to convince people to believe in Christ will seldom be successful. There needs to be a sincere desire to seek the truth. Your time would be well spent demonstrating an attractive vision of the Savior through your life and be ready to discuss and answer their eventual questions. Those who are indifferent to Christianity--or even hostile--need to to see a dynamic relationship with Jesus Christ which faithfully follows 1 Peter 3:15: a life that sanctifies Jesus as Lord of their lives and is always ready to give an answer for the hope that they have and yet do so with gentleness and respect. Evidence and arguments will rarely make an impact unless there is an inquisitiveness first.
And yes, we must be saved to spend eternity in heaven. Be careful however, about being certain in judging someone's salvation. Even the greatest saints still sin and while there should be a pattern of good works to verify someon's salvation, we all go through periods of rebellion. Also, only Christ can judge the true condition of a person's heart.
If a person truly thinks they are saved and seeems to at least have a basic understanding of salvation through Christ, we should take them at their word until something incontrovertible happens that leads you to believe they have been living a lie. I'm just asking that you be careful in making these kinds of judgments and that as far as it depends on you, be at peace with all men (Rom. 12:18).