Get there early. Don't skip any fights. The first UFC event I went to was UFC 83 in Montreal and the 2nd prelim was some HW that was 2-0 and nobody had ever heard of named Cain Velasquez!!!! I had heard he was really good and had so much trouble finding opponents willing to fight him but seeing him move like a WW and destroy his opponent was amazing. Then in retrospect being able to say I saw Cain live is kind of cool.
Don't drink too much too early or you may not remember the Main Event!!! Also it can take forever to get to piss if you wait until in between fights as there is lots of beer flowing and the lines get long.
Three things stand out from UFC 83. GSP really fucked up Matt Serra, Velasquez was a beast, and that was the turning point for me with Nate Quarry. Was never really a fan of his until that night. I can't recall a single fight where I have ever actually laughed out loud as much as that one. Except for maybe rock 'em sock 'em Sanchez vs. Ross Pearson (I think). At one point Sanchez was chasing Pearson across the octagon spamming one-two's, caught nothing but air, and got countered every single time. Fuck that was funny, and to be fair it could have been Matt Riddle. I was hammered at the time.
I have attended two live events, and yes, the atmosphere is electric and the energy is wicked. I was very close on the floor both times, and it really was worth attending live just for the experience. That being said, I actually prefer to watch at home now. Better view, I can do or say whatever the fuck I want, food and drink is way, way cheaper... and I don't have to worry about all the heroes hopped up on liquid courage.
Also, Bruce Buffer could have played a hobbit or dwarf in Hollywood. Damn that guy is some short in real life. Hit up a bar with Jeremy Horn after Rory MacDonald vs. Tarec Saffiedine, and man... that dude was fucking hammered. He could barely speak, his eyes were going in different directions, but he was really cool. A hot chick would walk by and it was like Charlie Brown's parents were speaking beside me, it was just one long slur with rising tones, lol.