There are only a things you need to focus on to survive early game and get to the easy part (late game) as an adc
- Don't die.
Obvious I know, but even when obvious, far too many people die before the 10 minute mark. If you can last until then without dying then you are playing your lane correctly. There are rare situations when this its okay to die, very rare. This rule is so important so so so very important.
- Last hit
CS, Farm, Last hitting. The 2nd most important thing you can do (second to staying alive).
Melee Minions can take 2 hits from a tower and then your AA (auto attack)
Caster Minions require one AA, one tower hit, one AA
CS is far more important than kills, if you can get a kill take it but if you are focusing on kills so heavily that you are behind 30cs you will hurt later in the game.
- Understand your support
An adc heavily relies on their support to do well in lane. Understand the synergy between you and your support, understand their weaknesses and strengths.
This also applies to the enemy team.
If you are Kog'Maw and Sona vs Corki and Leona, you will want to avoid fighting AT ALL COSTS. This goes back to rule #1: Don't die.
- Runes
Your runes play a big role in your early game. Getting a bonus 8-15 ad from the start helps a lot when farming. (AD Reds/Quints). Armor Quints and typically Mr Per Lv Blues.
- "I am behind"
If you die first in lane there is a 99% chance you are officially behind, don't let your pride swell up saying "he just got lucky, it won't happen again". If you think that way it WILL happen that way again. If they are zoning you (not letting you cs) let them zone you and politely ask your jungler for a gank, nobody wants to gank for a whiny bitch. Staying alive is more important than farming remember that. You can farm later, you can't take back a death.
I hope you use this well
I don't know why all bullet points came out as "1."