If some of you guys didn't know, League of Legends offers 3 free skins + champs.
* So no need to buy the champions first, you get them for free if you haven't got them *
For Riot Girl Tristana skin - You have to like their facebook page and type your summoner name.
if you are on NA server proceed here - CLICK
if you are on EUW server proceed here - CLICK
For Unchained Alistar skin - You have to subscribe their Youtube channel.
if you are on EUW server proceed here - CLICK
if you are on EUNE server proceed here - CLICK
if you are on NA server proceed here - CLICK
---------------------------------------------------------------------------
Few years later they also added Garen + skin.
For Dreadknight Garen skin - You have to follow their Twitter account (if you don't have Twitter account, just make one quickly ;))
For EU server proceed here - CLICK
For ANY OTHER server proceed here - CLICK
Enjoy :)