I usually do it online, often along the way during the day. I like having online access so I don't have to be at one computer to enter the info -- I can do it from home, or work, or when travelling. Sometimes when I have no internet access (the horror!) I write things down on paper to remember for later -- or just to keep me aware as I go along.
I like that computerized versions keep track of all kinds of statistics for me!
I used to use both, but now I try to keep it as much on the PC as possible. I usually plan out what I'm going to have to eat ahead of time, so that's not a big deal. But, if I end up eating something I haven't planned for, I might write it down so I can record it later.
I use fitday online. I generally plan my meals/snacks out ahead of time but modify during the day as needed. I like the online version so I can update at home/work/wherever I am. I've used pen and paper but with the computer programs you just store your custom foods once and boom done forever.
I use the daily plate, unless I won't have access to a computer for a while, in which case I write everything down so I won't forget to enter it later.
Neither, actually: I have a program for my Palm device. It's the best of both worlds. It does all the work, and it's portable.
it has a huge database of foods that I can add to
it keeps track of calories, carbs, fat, protein & fibre
it tracks my weight and my glasses of water every day
it has a database of exercise and I can add my own
it can calculate recipes for me
it can track measurements and blood pressure, too
It's also available for the PC, and there is a trial version that is fully functional, but won't let you add foods, if I remember right. And it's not expensive. Google Keyoe Diet and Exercise Assistant.
I have an Excel spreadsheet that gets more complicated the more I play with it. I don't work, so most of my week is spent near enough to my laptop to do the entry. And, since I cook most all of our meals from scratch - and try new recipes all the time - all the pre-entered stuff on the other sites wouldn't do me much good.
I use both the computer and pencil and paper. I use the pencil and paper during the day, and at the end of the day, I go to www.sparkpeople.com and record my food and other activities there.
i downloaded calorieking.com for my pda. Its great...lots of foods including many resturants...the only thing i wish it did better was adding recipes (ie if you have a recipe that doesn't have calorie/fat etc, you could enter all the ingredients and it would give you that info) but love my pda