See, I'm hesitant to answer this because if I make it sound too good, I don't want you to feel like you're missing anything. But if I make it sound too bad, it'll be obvious that I'm bullshitting you. So... honesty.
When you first get started, you'll notice your skin becoming warmer, and maybe a little bit of numbness in the face. That's the indication that you've hit the buzzed stage. The buzzed stage is by far the best, all downhill from there. This is where the "reduced inhibitions" you hear so much about start.
At the buzzed stage, you're still in control, but you laugh much more easily, about pretty much anything. Any joke is funny. You also start to talk a lot louder for no apparent reason, and you're much less concerned about what people think of you. This is the stage where you'll be likely to just walk right up to the hottest girl you see and ask her out with no worries at all.
Past that, you get to the drunk stage. Vision gets a little blurry here, speech starts to slur a bit, and the inhibition loss becomes more severe, sometimes to the point of being problematic. This is the stage where you'll see people doing those stereotypical drunk things like taking off clothing and dancing on tables. It's funny at the time as long as everyone else is drunk too, but you pray the pictures don't find their way onto facebook. Depending on your level of tolerance adn the combination of things you've had to drink, if your'e going to get sick, this is where it starts. It's not too late to turn back at this point, but the inhibition loss tends to make you forget that.
Next, comes plastered. This is where it stops being fun for most people. Speech is very noticeably slurred at this point, it's difficult to get around without assistance, and you've gone from being the life of the party, to the guy in the corner trying his best not to pass out. Needless to say, it's not really fun from this point on. Trying to sleep at this point can be problematic because of "the spins". This is the phenomenon in which lying on your back and closing your eyes causes a sensation like the room spinning, causing severe nausea. The cure for this is to sleep on a couch with one leg firmly on the floor. That stops the sensation just enough to allow sleep.
If you manage to get past this (usually because you drank so much before the alcohol hit your system that you proceeded quickly through the plastered stage), you get to the blackout stage. Not everyone hits this point, but for those of us that it's happened to, it's not something you ever want to happen again. This is what causes all those stories you hear of people waking up in gutters and not remembering the previous night.
Hopefully that about covers it. In summary, it's not the best thing int he world and if you choose to never do it, you wont' have missed all that much. But it can be fun in the right setting, with the right people,and the right mindset.