Be better at League of Legends
How to improve?
First of all you need to know that self improvement is most important thing you can do.
From there you can: Identify your biggest mistake, find one problem for you making that big mistake and then practice fixing that only issue.
There are definitely many issues that you can think of, like:
Teammates losing lane? Your dying too much? You don't have enough gold? You losing map control? Don't have map awareness?
Overcorrecting your issues is the Best way to improve yourself every single time! And remember don't forget to try new tings after learning, it's always important to test your abilities.
Objectives
As we all know the main objectives in League of Legends is to destroy enemy turrets and nexus. But there are also side objective like Baron Nashor and Dragons and Rift Herald.
Baron Nashor
Baron Nashor is the most powerful neutral monster on Summoner's Rift in League of Legends. Killing Baron grants Hand of Baron to all living teammates for 210 (3 minutes 30 seconds) seconds or until death.The buff gives bonus attack damage and ability power. Also you get Empowered recall (Reduces channel time by 4 seconds and a successful recall restores 50% of your champion's maximum health / mana and grants 50% bonus movement speed for 8 seconds). Last but not least you get an aura that greatly increases the power of nearby minions.
Dragons
Dragons are also know as Drakes. Dragon is the second most powerful neutral monster on Summoner's Rift in League of Legends. Slaying Dragon grants the team one of Dragons Slayer buffs.
There are total of five Dragon:
Infernal Dragon: Slaying Infernal Dragon grants +8 / 16 / 24% increased attack damage and ability power.
Ocean Dragon: Slaying Ocean Dragon restores +4 / 8 / 12% of missing health and missing mana over 5 seconds if not damaged by champions or turrets within 8 seconds.
Cloud Dragon: Slaying Cloud Dragon grants + 25 / 50 / 75 bonus movement speed while out of combat.
Mountain Dragon: Slaying Mountain Dragon grants +10 / 20 / 30% additional damage as true damage to Epic Monsters and turrets.
Elder Dragon: Slaying Elder Dragon grants The strength of all elemental dragon buffs is increased by 50% for the duration and (45 × Elder Dragon slain) (+ 45 for every elemental dragon stack) true damage on all spells and basic attacks against non-turrets over 3 seconds.
Rift Herald
Rift Herald is a powerful neutral monster on Summoner's Rift in League of Legends. Slaying Rift Herald drops a relic in the pit for some time that can be picked up by one member of the slayer's team, granting them Enchanted Recall and the Eye of the Herald. Rift Herald will despawn permanently at 19:45, or 19:55 if in combat, with Baron Nashor spawning in the same position at 20:00. The Eye of the Herald, once collected, replaces the Trinker of its owner. Activating the Eye will crush it, starting a 3.5-second channel that, upon completion, summon the Rift Herald to push the respective lane.
Turrets and Inhibitors
Inhibitors are structures that block the training of enemy super minions in their respective same lane. Inhibitors have 4000 health and no armor or magic resistance.Only minions spawned in the destroyed inhibitor's lane receive additional attack damage while the inhibitor is down.Destroyed inhibitors respawn after 5 minutes, resulting in Super Minions no longer being trained and the removal of normal minions' bonus health.
A turret, also called a tower, is a heavy fortification that blocks the enemy's minion waves and champions path to the nexus.Turrets are one of the core components of League of Legends gameplay, providing damage, vision, and general control of the surrounding map. All turrets have 1095 sight range and 775 attack range. They grant true sight, allowing you to see all traps and stealth units that are nearby. The first turret destroyed yields 300 total bonus gold to its killer's team. There are 11 turrets in Summoner's Rift. The weakest tower is the first in bottom lane. Turrets deal bonus damage to melee and caster minions so that melee minions generally die to two turret attacks and one champion auto attack, and ranged minions die to 1 turret attack and 2 champion auto attacks. Turrets deal 70% damage to siege minions (Cannon minions). Be careful when fight under the turrets because every next turret attack you take will be more powerful.
Remember: The outer turret must be destroyed before the inner turret, and the inner turret before the inhibitor turret!
Minions
Minions are units aligned with one of the teams. They spawn periodically from their nexus and advance along a lane towards the enemy nexus.
There are four kind of minions:
Melee minions: Use melee attacks against their enemies. Three melee minions spawn with each minion wave
Caster minions: Use a ranged bolt of magic against their enemies. There are 3 caster minions in each minion wave.
Siege minions: These minions deal more damage and have more hit points than regular minions. They also receive only 70% damage from turrets. They use a ranged attack against their enemies, However, their range is lower than that of caster minions.For the first 20 minutes, 1 Siege minion is spawned every three minion waves between the melee and caster minions. After 20 minutes, Siege minions spawn once every 2 waves and from the 35th minute onward, Siege minions spawn every wave to accelerate the game pace by making pushing easier.
Super minions: In the classic game mode, they will only spawn in lanes while the enemy inhibitors on those lanes are down. In that case, one super minion will spawn at the front of each new minion wave. If all inhibitors are destroyed, a second super minion will spawn in each lane behind the first one.While super minions are spawning, no siege minions will spawn in that lane.Super minions will stop spawning shortly before the enemy Inhibitor is going to respawn to prevent the Inhibitor from instantly being destroyed again due to them.
Remember: Minion stats increase at 1:15 and every 90 seconds after that. Caster minions do not gain health past 26:45, effectively capping their maximum health to 425.
Money
Gold is the in-game currency of League of Legends. It is used to buy items in the shop that provide champions with bonus stats and abilities, which in turn is one of the main ways for champions to increase their power over the course of a game. To get more gold faster you need to kill minions. Champions also passively generate gold, which can be increased by runes, masteries and items. Passive gold gain does not activate until minions spawn.
Starting gold:
Summoner's Rift: Champions start with 500.
Twisted Treeline: Champions start with 850.
Howling Abyss: Champions start with 1400.
All items can be sold back at the shop for 70% of their total cost, so try to always buy correct items.
Practice Tool
If you want get basics down, the best thing you can do is to go in Practice tool.
You can learn:
Champion mechanics and combos.
Jungle practice
Endless last hitting
Item build and DPS checks
Map familiarity (ward placement, wall flashes, etc)
And here is map awareness training video for some of you!