It's one of the great choices people make when taking pictures, and there is truly no right or wrong answer, so do you make sure the shot is composed correctly when you snap the picture, or do you go for the as long as everything is in frame and the angle is right you can fix it later?
personally i use the crop it later method, mostly because of what i shot, i don't take a lot of posed pictures meaning that my window for capturing a particular moment is very small, additionally even in the past when i did compose the before shooting, i found that i went in for a small crop afterwards anyways just to improve the picture. Quality isn't a issue, cameras and even camera phones now a days have high enough pixel counts to look good even after a 20%+ crop for uploads on Facebook.
Just for side information, i use a Panasonic GH2 + 20mm F1.7 primarily
So what's your way?
Your right, when posting photos to facebook it doesn't really matter.
I always try to get the photo as perfect as possible with just the camera though... The less post processing done on an image, the better. In general, peoples camera skills are pretty lacking because of the safety net of Photoshop.
i use the crop now method as best i can, though it's more difficult without gridlines on a dslr.
@SLUSHIE: I don't think photoshop is a safety net at all, i think that most people don't know how to use ps and it can look complicated.
I find that the "less post processing" to be untrue, but i'm guessing you might be talking about filters? most pictures i shoot, i will go in and tweek the colours, contrast and levels/curves to really get the most out of them.
@norman: on the GH2 theres a fabulous EVF so i overlay the grids, but i found that once i understood how and why the grid system works the visible grid became a limiter to improvement.