1) Don't let ragers get to you. 2) Play Bots for the first little bit, enough for you to understand the mechanics of moving around, and taking down objectives, then go fight real humans. 3) Take it easy, League is a fairly difficult game to pick up, there are A LOT of champions and A LOT of items. Don't get stressed out if you get beat
BlazBlue CSX: Mu-12 and Taokaka youtube.com/user/Shinius
Don't start if you don't want your life sucked out, (if you have even a miniscule part of you that has an addictive personality).
Ok I lied you can get tired of the game pretty easily but just basically learn everything, just learn how every skill works on every champion, etc. Play bot games and play as every champ and think about what they do and one character can do when another does X move, etc. Counterplay mechanics.
Also focus on last hitting skills, practice in bot games and try to get the last hit on every minion to get gold, it's sorta dull at first but it's required to actually play the game at any sort of competitive level (aka not lose majority of games).
Then also practice just landing your skills (aiming), general mechanics like that. Also learn what smartcasting is (automatic cast at position of mouse cursor), and try it on skills. Do all this in bot matches of course.
Go on solomid.net, lolpro.com, or mobafire.com to find guides on the champion you plan to play. They'll tell you what skills to rank up in what order and what you should build. Once you learn more about the game you can decide what item is best to build in what situation, but until then just stick to the same build.
Look up a bunch of noob guides.
Mute everyone in every game or have thick skin because people will say unspeakable things to you for being new and not good at the game.
Go into your options in game and reduce the size of your HUD. If you're on the top of the map and you're trying to attack someone below you a large HUD is going to completely screw you over.
first try getting used to controls with recommended champs with basic bots. i would suggest picking taric and learning the basis by playing safe. dont forget to read the skills' descriptions so u know what they do also make sure u checl the map when u hear the pings' little noise so ppl dont say u dont cooperate most important of all, just find a legit site and search a guide so u dont build crap