When I put up a link to my site, do I want to write:

http://www.mydomain.com

or

http://mydomain.com

or

www.mydomain.com

or

mydomain.com


I know that technically all of those are different domains, and link juice is diluted by using all 4 versions. (Am I correct on this point?)

If so, which format is best?

And how can I put up a 301 redirect for all the others- and is that a good idea?

So many questions- thanks!