How do you tell a best friend the truth?

Just like the title says, How do you tell your best friend the truth? Simple, you just do it! slap some sense into the person no matter what it takes. I had to do that today with my friend jarely. She hits me up saying that she needs to talk to me and I listen to what she has to say. Its all about her ex cris who played her big time with one of my friends. the only reason this happened is because she lives in north carolina for the moment and he lives here. so we talk for about an hour or two about cris and how she has to let him go. it went on and on, the girl still wants the guy, BADLY. I tried knocking some sense into her and in reality it worked. I love this girl like a best friend and maybe a sister and i really didn't want to see her get hurt. At the same time, I have other feelings for her too. I have to think carefully about that though. Other than that, always tell your friends the truth, the whole truth, and nothing but the truth. It helps set you free of all boundries and emotional pain you may be going through, or it just helps you out in a big way, but seriously if your gonna play someone, do it right. because in reality, cris did it so slopy and he's stupid for doing it too. Well, sucks for him. HAHAHAHAHA!