Hey folks!
Sometimes finding good information about specific champions, or tactics within League can be difficult. Post your favorite League of Legends guides here, so we can share the knowledge! These guides can be video, written, or whatever!
For instance, I found this guide to be pretty useful when learning to play Nami! https://www.youtube.com/watch?v=ZxL4nPd9qs8
What guides to you find useful?
This guide speaks to me on a spiritual level: http://www.solomid.net/guide/view/126389-garen-build-guide-fighter-by-ouroboro. SPIRITUAL LEVELS.
https://www.youtube.com/watch?v=nfWs_fl8El4 Ahhh, classic.. ;)
EDIT: AND that, of course. https://www.youtube.com/watch?v=r-fIOrUTIOQ
And who can possibly forget the good ol' SivHD guides..! ;D
This is the best guide I've come across and would recommend it to anyone below level 30. It goes over all of the basics without too much of an information overload.
Best and most accurate guide I ever wrote: http://forums.na.leagueoflegends.com/board/showthread.php?t=305837
http://forums.na.leagueoflegends.com/board/showthread.php?t=28942
The original and best.
Number 1 super happy fun guide to playing the MFing Cho'Gath.
This one is by far my favorite. I find all of gbay's videos to be informative and helpful, but this series I found to be the most enjoyable of the lot.
shorter guide https://www.youtube.com/watch?v=LRS726yRwiI
longer guide https://www.youtube.com/watch?v=xTMUO2AyrV0
Sauron's guides remain the best source of Dominion information despite dating: http://forums.na.leagueoflegends.com/board/showthread.php?t=2244698 http://forums.na.leagueoflegends.com/board/showthread.php?t=2152948
They're particularly handy because of how much information the official page leaves out (champion ability changes, accurate item information, etc) and the complete absence of any sort of signal boosting for what we create as replacements. It's a pity we don't have a place to cross-post that work; "Maps and Modes" is as much a dumping ground for random as the old GD and it can't even bother to pretend it's inclusive with this URL: http://boards.na.leagueoflegends.com/en/c/ summoners-rift
One on 
! Oh wait...their aren't any seriously helpful ones... ;~;
http://www.youtube.com/watch?v=QXd-8wsZbLg&list=UUAnY0ffucBC8fZa_xMwCF4Q I love when trico does guides, he is so funny and entertaining (especially when he uses impressions like these)
Best guide hands down. http://www.mobafire.com/league-of-legends/build/mantheon-nipple-inspector-209448
Carried me to Master tier, i heard this is the way phantoml0rd got big.
InvertedComposer 
guide. This guy knows EVERYTHING there is to know about
http://www.lolking.net/guides/38109
It's not a champion guide, but I still consider it the best one I've read. http://www.solomid.net/guide/view/29322-generic-build-guide-by-tapobu It looks at playing league from a more broad teamwork perspective. Providing information and tips for facilitating teamwork, interacting with team mates (the good and bad), as well as tactical tips for identifying and exploiting player tendencies (allied and enemy). Perhaps the most valuable part of the guide, is the application it gives for dealing with toxic players (from the rage-quitter, to Troll, to OMGWTFYOUSUCKREPORTED!). I've recommended this guide countless times before, and I will continue to do so in the future. :D
best guide: http://www.solomid.net/guide/view/126536-rengar-build-guide-fighter-by-ryanchoi
if i start snowballing i dont stack so much dorans(2 most) and I prefer: ie+triforce+hydra+yomus+lw+mobi boots with alacrity(replaceable with black cleaver or zephyr) as my endgame build.
This is an older video, but helped me as I was getting better at the game and used to controlling the flow of creeps in a lane!
also this guide already won guide of season 4.
My favorite guide is a guide from mobafire Its called "All mobafire guides are without flaw"
:^)
Also 
/
guides involving basketball hoops
Staring 
as "Shaq's mom"
Staring as Magic Johnson
Support is ez pz
http://www.youtube.com/watch?v=e1CLbAevPqo Master Zed with a new energy rune based build. http://www.youtube.com/watch?v=Mbr8Rcktsu4 Shen is the new king of ganking junglers.
Shameless plug time! 
http://www.lolking.net/guides/297151
For reals though, this Twitch guide is very good and I found it immensely helpful. 
http://www.lolking.net/guides/276787
A Guide to Understanding the Dynamics of Bot Lane Most controversial guide I've ever come across, depending on who you ask it is the best thing they ever saw, or it is simply 'basic' whatever the case, someone surely spent a lot of time and effort writing it, and I've yet to see any outright negative remarks about it.
So much knowledge and reasoning, concepts, how to apply them, how they work, why they work, mentality, runes, masteries, summoner spells, positioning, theory of winning a lane, play styles, lane types, I could go on, but what it doesn't have is matchups, but then again doing the math that would require more than 900 different matchups in bottom lane alone, so I guess it's fine considering it does explain how to deal with the different champion types and play styles.
http://forums.eune.leagueoflegends.com/board/showthread.php?t=723240
Once upon a time I started making guies http://boards.na.leagueoflegends.com/en/c/champions-skins/fI5a4fls-chickenwraps-guide-a-week-week-1-galio http://boards.na.leagueoflegends.com/en/c/champions-skins/pPIRv3cy-chickenwraps-guide-a-week-week-2-ahri
Also I know things: http://boards.na.leagueoflegends.com/en/c/miscellaneous/aE2d7x74-i-am-a-crappy-player-that-knows-almost-everything-about-league-ama
HashtagSelfPlug
But for real, I haven't come across a guide I truly found to actually help me out so much as just to double-check with them when I first started playing to know if I was on the right track or not with my builds, except for:
https://www.youtube.com/watch?v=0kxGQ3gWdrM RIP Shurelia
https://www.youtube.com/watch?v=r-fIOrUTIOQ
Hackee is a nooblord. Nooblord. Nooblord. Nooblord. Nooblord.
How is: http://www.lolking.net/guides/208072 "Some Call it Magic: Lucian"
Def. best guide for a champ.
Some of these are old, and they might not be "guides" in the same sense as the others here, but they're probably my favorite:
I really like HuzzyGames guide for Aatrox. It helped me a lot when learning him: https://www.youtube.com/watch?v=NjdWiaVdR8U
Mine! lol http://www.lolking.net/guides/225231
needs rework and updates lol but MINE! lol
http://www.lolking.net/guides/308138
Shameless plugin.
