Originally I started off using Ratebeer.com years and years ago, and have racked up hundreds of reviews in the time, but it does get to be a bit of an effort after time, and there are hundreds more beers I've never gotten around to rating. Having said that, it's good because you score it and compare your ratings and oppinions against others.
When I travelled Europe for a couple of months in '07 and '09 I actually had a little notepad with me and would just jot down (rarely legiably) the names of beers I tried and what I thought, and often take a photo. This was ok, and I got some good notes on the beers I really liked but yeah, it gets to be a bit of a task, especially with some many "generic green bottle lagers" out there, you tend to be writing the same comments each time! But hey, it's like a treasured memory now, and I can look back through it and remember those locales, drinking that beer and the experience.
Apart from that, what I take most seriously is homebrew notes. I've been somewhat systematically formulating Word documents full of notes on every beer i've ever brewed (and I try to be honest), and every beer I get to tasting from other brewers through Caseswaps and whatnot over the years...up to 441, which is suprising.
Having said all that, I don't think its necessary to sit there and write down a bloody novel about every beer you try, just one line can do it, like "Pale gold body, persistant white head, citrus hop aroma, medium bodied, some caramel malt on palate, firm bitterness to finish".
As much as it's a whole lot easier to just write down the name of a beer and give it a score out of 10 say, in the interests of evolving your palate, I think it pays to articulate some sort of description just to get your mind considering flavours, and textures, and ultimately figuring out what it is, and how it got to be in that beer...which will eventually translate to becoming a better brewer!
