modeling eficiently is very broad and vague, depends on the user's workflow.
one thing to do is to know your tools and specifically what they can do.
once you know, you then have to ability to judge when to use them and what is the best tool for whatever you are using.
but start out small then move on to more complicated mesh or forms. most people start with learning organic human modeling, thats a good way to start imo, find some good tutorials and spend some time working.
as for a good site, i think this site has some good stuff.
there are alternative written tuts on www.learningmaya.com