im still new myself, relatively, but i'd say first is getting the basics, comprehending each lane's role, trying out all of them (top mid bot jungle and last but not least support) at least a few times, try different champions without focusing on one in particular.
when you hit level 30 , dont insta go ranked, play a lot of normal games , and find your calling, the lanes and champions that you like and find yourself doing best with. after you'be gotten the hang of the champion, and find your perfomance getting consistent in normals, aka not burdening your team and having an influence on the game's flow (a postivie one tho :P) , then go for ranked. after that, it's mostly the same thing, but more of honing those skills.
also, please dont flame. we all lose it when someone picks a jinx top sometimes, but keep your cool, its a game, dont flame, dont flame, dont flame, if you are flamed, still dont flame. be nice, and say glhf . oh, also go to your settings and activate the enemy team chat , so you use /all freely.
uh whatelse, make sure you watch a lot of videos, tutorials, preferably ones that contain the specific champion you're learning, or the lane you want to main . dont obstinate over yasuo and zed like 90% of the newbies either.
also, whens someone deserves it, honor them. dont be stingy.
some easy champions include ashe in bot, annie in mid, garen in top, maybe xin zhao jungle or amumu, soraka/sona support
anything else would be to have fun :) its the main purpose, and dont you forget it