If I don't know you, I would say 'teşekkür ederim or teşekkürler'. If I know you, or if I want to keep it short, I would prefer 'sağol'. Actually they are not very different, you can use them all in any situation you would face.. no one is going to look at you with weird eyes; because they are all express the same with very very small difference

*Sağol: Informal. You can use it when speaking with your close friends, family members or relatives.. Your friend gave you X, you say "sağol" (or teşekkürler/teşekkür ederim) Sağolun/Teşekkürler/Teşekkür ederim depend on the person you are talking to. Sağolun: (Siz) sağol-un. "-un" particle indicates to "Siz"("you" in polite lang and "you" in plural form). Your friendS gave you X, you say "sağolun" (informal->"-un" indicates to more than 1 person) Your boss gave you X, you say "sağolun" (formal ->"-un" is used for politeness) (or teşekkürler/teşekkür ederim) Teşekkürler/Teşekkür ederim: You can always use this, formal or informal it doesn't matter. You can use when speaking to your friends or boss. Teşekkür ederim is the most polite one Formal to informal: Teşekkür ederim=Teşekkürler=Sağolun > Sağol Polite to impolite: Teşekkür ederim>Sağolun>Teşekkürler>Sağol In short: Except for "sağolun" (in politeness form, not plural), all are interchangeable. People you are close to: Teşekkürler, teşekkür ederim, sağol People you don't know/formal:Teşekkürler, teşekkür ederim, sağolun

Teşekkürler is dominant. It depends on you. These type of things are Arabic, teşekkür is arabic, derived from şükran, şükür. Sağol means, "i wish you stay healthy". "Teşekkürler" is formal. You can use it at the end of your emails also. "Teşekkür ederim" is general. Use it everywhere. It means I "personally" thank to you. "Sağol" is used in military service too much. Commander asks "how are you soldiers?". They are answering "sağol!". "Sağolun" is; I wish you to learn turkish very soon, then you can answer "sağolun" because we are not familiar each other. If we know each other or if you think you are high level than me, you can say "sağol". Or after a surgery or sickness, "get well soon", then "sağolun, teşekkürler"(use both), or "sağol teşekkür ederim". Also you can use with "çok": çok sağolun, çok teşekkürler, çok sağol, çok teşekkür ederim.