So i really want to start watching this

I would always start with season 1. The seasons built up on each other and you would often not get the joke or story if you skipped episodes.
Another advice: Don't google anything anymore about the show! ;)
The show lives on their twist and you could get easily spoiled with unwanted information.
For the quick catch up: as soon as the show gets you, you won't be able to stop so you will really quick catch up. On good days I make one season in a day :P

Have fun with the show, it is the best <3

Start with Season 1 - isn't it always better to start at the start, and not skip anything? I know there's loads of catching up, but you will get there.

I don't think there'd be anything you need to know beforehand, the first episode explains the initial scenario well. It's not like the series is a spin-off of something else.

For Season 9 we already had our mid-season finale and we're on break till January 14th so we're a good deal into the season. Supernatural is a good show and I promise you won't forget it (I can't promise you won't get your heart broken though) Anyways I would really start with Season 1 because if you watch it from the beginning as the storylines go on, you really understand the whole show, and the relationship between the two brothers, their personalities, and their backgrounds. Then that way you get to kind of fall in love with the story and the characters. You'll laugh, you'll cry, you'll scream, that's how good this show really is and that's how emotionally involving this show is. So until Supernatural shows the rest of the seasons, I urge you to start like right now!! All 8 of the seasons are really good, and you gotta catch up on the first half of season 9 while CW has the episodes online. You have time though so take your time through it, but I promise it's worth it!!! :D

This show will take over your life. And it will cause much pain and tears but I promise it'll so be worth it. Best TV show ever.