How do you copyright your work?

You don`t have to fill any forms to copyright your work. As soon as you take a photo copyright belongs to you. Hope I helped

yeh from what ive heard there is no full way to copywright your work
if you're putting them on your own website then watermark them using photoshop
also if there is a dispute with someone else using your photos its never worth trying to get anything out of it because its a waste of time & money to get to the bottom of it
but if there is a dispute you want to follow through with then keep the original files you have uploaded to your computer & it will have under the info the date you uploaded it to your computer as proof of who had the picture first basically

Ok great thanks a lot, so there's nothing I have to do to copyright my photographs other than take them in the first place, well that makes it a lot easier.

A quick question though, when selling photographs to clients should I be asking if they want them for just one time or if they want the copyright? Presumably I'd be paid slightly more if they wanted the copyright for the photographs too?

Putting the copyright symbol and your name/company name on the image - say if it's on your website - won't hurt to remind people.

And yep I'd say quite a big difference in cost. Places like Getty etc will charge based on where you use it, circulation of that image (so if it's on a billboard how large is the image, how many billboards, or a mag what's the circulation of that mag etc) and you pay for a licence to use it on that one-off basis. Outright copyright purchase to do whatever they wish with for however long should therefore be substantially more I would have thought.

Down to you to decide what those values are though obviously.