Best advice would be to surf a few of larger link sites like
Link O Rama New Sites and look at the new site listings. That should give you a pretty good idea of what's listable
Nothing personal...it's gotta be said though, never directly copy another site...use it for inspiration and ideas only
Also, always read the rules of the sites where you'll be submitting. For the most part, if you're listable at Greenies, you're listable anywhere...which is why I suggest starting there.
Lastly, when you've got a sample ready...post it up on the forum and ask for review, you'll get honest opinions here