how are LP(League Points) acquired?

There are 2 things you have to understand if you want to know how League Points are distributed.

The League System
The League System was introduced by Riot Games at the start of Season 3. It's basically a system that is divided into divisions (1-4) and tiers (Iron,Bronze,Silver,Gold,Platinum,Diamond,Master,Grandmaster,Challenger). Now every 100 LP you go up a division or if you are in division 1 you will go up a tier. However note that the league system is not your relative skill.

The Elo System
The Elo System or MMR (Matchmaking Rating) is your relative skill. It calculates the average MMR of your and the enemy team and then you will gain elo based on the difference between your elo and the enemy teams. For exampe if your Team Elo is Higher than the average of the enemy team, you will gain less Elo on winning and you will lose more on losing the game. Note however that the Elo rating is hidden and there is no way to find it out with 100% accuracy.

Now the thing that determines the LP you gain is actually the relation of your position in the League system and your MMR. Each division/tier has an MMR that should be reached. Silver 4 with 0 League points is exactly 1200 Elo. You can however be in silver 4 with more or less than 1200 elo. You will also gain more LP if you are above the average elo or less if you are below it.

Why can I have a higher/lower Elo than my division?
It's mainly because of the promotion system. You can Always win 1 of the promotions and then dodge the queue in the next game. Queue dodging will lower your LP but not your Elo. This means you will constantly gain bonus Elo while you are "stuck" in a certain divison. Another big factor is duoqueuing since a disparity in MMR will influence your LP and MMR gain and loss.

LP is gained based on Win/Loss only, and is based on the relative skill of all parties involved.

No in-game factors contribute to League Points, except winning the match itself.