If your friend is making poor choices, do the following:

1. Talk to them. You can't control your friend's life, and you can't force them to make choices that better fit your plans of what is right and wrong for them. However, you can do what you are supposed to do, and be their friend. Sometimes it takes the word of a friend to open up someone's eyes to the stupidity of their choices. If your friend is doing drugs, being slutty, damaging a relationship, or something else that could have serious consequences in their life, it is best to open your mouth. You would not want to be blamed for not helping them see their folly until it is too late, so set your fears of rejection aside, and let them know where you stand, and how you feel about things.

2. Explain your concern. When you talk to you friend about their choices, be clear about why you have a concern, and that you are concerned. You do not want to condemn them, or tell them that they are wrong and you are right. Rather, simply explain to them the reasons for your feelings, and make sure they know you care about them enough to take the risk of confronting them about the situation. If for example, they are into drugs, explain that you get their need to try new things, but you do not want to see them mess up their futures, or become addicted to something. Show true concern, and care for them, and it will be hard for it not to reach them. Just be careful to keep judgment and a "Holier than thou" attitude out of it.

3. Stand by them regardless. When a friend is making poor choices, it can be hard to watch them flush their life down the toilet, or do something you know they will later regret, but part of being a true friend is being for them regardless. Not everyone is on the same time table, so the best thing you can do is just remain their friend, stand by them, and be there for them. It does not mean you have to approve of their actions, or support their folly, but means that they need to know they can always count on you if they need a shoulder to cry on, or someone to turn to.

No one likes to see their friends make poor choices, but the only person you can change is yourself. So, be a good friend, and lose the judgment, and you will have far more chance of influencing them for good.