paulalford on "Best way to Register New Users?"

I have read some older forum posts on the issue but nothing with WP 3.6.

I want a public blog, with anyone able to register and comment (with moderated approval of each registration AND comment). What is the best/safest way to handle this ?

Also, is there a plugin to add a 2+2=4 to the initial registration to prevent autobots?

Thanks
Paul