If you are using vim >=7.3.74, then you can actually put this in your vimrc:
set clipboard=unnamedplus
Which will automatically use the + buffer (the system clipboard) by default. Then to yank (copy), you just use the regulary command, etc.
I found this behavior to be fairly annoying, though, as commands like d put the text they operate on into the default buffer, which meant I couldn't do a fastdd and paste a line from the internet, for example.