Tristana Lvl 2 All In

Needed:

Tristana
Support with some CC Morgana, Nami or a grab like Nautilus or Blitzcrank
Level 2 while the enemy laner are still level 1

Action:

CC their ADC
Rocket Jump over the ADC to slow them
Explosive Charge the ADC
Shoot them at least four times to maximize the damage from Explosive Charge
Continue autoing if it is safe to do so

Outcome:

ADC heavily chunked or dead

Things to consider:

Watch out for enemy supports with stuns as they can turn this on on you. Looking at you Leona and Braum.

Runes and Masteries

Get in the habit of checking sites like champion.gg and probuilds.net and keep your runes and masteries for your favorite characters up to date.

Also remember that you can change your masteries before a game starts. E.g. if you are playing Olaf and even though you might normally go

2 Block
2 Recovery
1 Unyielding
3 Veteran's Scars
1 Juggernaut

If you are verses a Gnar you are probably going to get more mileage out of Swiftness. So something like this:

1 Block
2 Recovery
2 Swiftness
3 Veteran's Scars
1 Juggernaut

or

2 Block
2 Swiftness
1 Unyielding
3 Veteran's Scars
1 Juggernaut

Depending on if you feel you would get more value out of the sustain from recovery or the damage reduction from Block an Unyielding.

Scrying Orb / Farsight Orb

Are your friend as an ADC. Going to Bot lane to catch up on farm? Scry that menacing bush near your position to make sure there is no lurking Rengar or Talon hiding in there.

Enemy ran into a bush? Scry that puppy to get vision on them.

Trying for a long range snipe. Scry the area to help with targeting.

The Farsight Orb (the upgrade to Scrying Orb) also drops a visible 60 second ward in the scryed upon location, so you can aid the team by scrying an area that you could be potentially flanked from without even having to go near the area.