An unpopular tip for beginners.

Forget youtube and tuition videos.

The best advice I will ever give to anyone is learn to use your ears.

Back in the dark ages when I started to play there were no video tutorials. You learned to play by getting a book, then when it came to learning your favourite tunes, you had to sit down with the record (and a year or two later the CD) and play it over and over until you figured out the chords. Sounds like a nightmare, but the great thing about it is that you trained your ears, so along with being able to recognise chord progressions by ear, you also learn the chord voicings - I got to the point where I can even recognise the position the notes are on the neck. I recently shocked myself by tuning a guitar from scratch after rebuilding and when I checked it with a tuner it was bang on.
I became disillusioned with playing in bands a few years ago, because it seemed everyone relied on tab to learn a tune. I got fed up of spending rehearsal time teaching people basic tunes. Give me a CD and I'll have the chords down after two runs through of a tune (usually), same goes for solos and melodies. It's not a special talent or anything magical. I'm an average guitarist at best.
Learn to listen. Learn the scales. The only limit then is how fast you can make your fingers go.
You'll also find that 99% of youtube is at best inaccurate.

Great advice! I am in the same boat, although I am much too young to be around in the record days

A few times I have told bands that i was applying for that I wasn't interested in having heaps of rehearsals (playing covers) as they weren't needed, I can learn the songs myself at home, they didn't even get what I was talking about, they thought I must be a shit player who thought he was better than he is or something

I don't understand people that can't work out a simple song by ear or tune a guitar themselves without an electronic tuner, they're the first couple of things you should learn I reckon

I have nothing against doing covers - I spent a fair bit in bands doing weak original material, which is even more uninspiring - but I have experienced turning up for a rehearsal to be presented with a wad of tab printed from the net, which was garbage. The inability to waver from the original key is another - a mate's band is covering an Aerosmith tune, which their singer quite clearly doesn't have the range for, but they insist on doing it in the original key....

I have a million n one gripes call me a grumpy old b'stard...

TIP 2 - Don't drown everything with REVERB!!! Nothing sounds worse than a band playing a pub and the guitar sounds like it's in a swimming baths! Even worse if you use delay as well. I never use reverb AND delay at the same time and I would rather use a delay to add a bit of ambience than a reverb.

TIP 3 - It might sound great in your bedroom, 99% of the time it'll sound crap with the rest of the band. Get into a habit of standing where the audience will be during a soundcheck or get someone you trust who will be completely unbiassed to do so to tweek your amp to get a good sound. I'm lucky, I have a setup that generally I don't use at home anyway, but also with it being a programable pre-amp, live sounds are set in stone, with minor tweeks done on the power amp - volume & presence.

TIP 4 - The song is EVERYTHING. Keep it simple.The audience doesn't give a shit what guitar you play, how many pedals you have, etc. If tap dancing is getting in the way of your performance, stop tap dancing.

TIP 5 - Distortion. Unless your genre calls for it, don't overdo it. I'm inclined to say the same for clean, too, especially with chorus. Spotlessly clean can be just as overdone as full-on distortion. If you use chorus, dial it down a touch - with all effects subtlety is the key.

TIP 6 - You are there to entertain the audience. Think of it like football. The most successful ones work as a team not a group of individuals. Looking at your feet is boring and it's boring to watch. Interact with your bandmates, scan the audience for interesting characters or (ladies, please forgive my sexism & adjust if you're a female muso) do some 'talent spotting'. Having fun and interacting with the audience is as important, maybe more so, than playing a perfect set. If you're on Facebook, there's a brilliant example of how to entertain an audience in a clip by Dan Brown - also on youtube, I believe - Creep by Dan Brown. For me THAT is what entertaining an audiance is about - believe me, NOTHING tops the buzz you get when the audience sings along... NOTHING!
Oh, and long guitar solos are boring, as well, so IF you must do one, drop a bit of humour into it., eg. drop in the Archer's theme in the middle or some other widely recognised tune - audiences like guitarists who don't take themselves too seriously.

That'll do for now.