It's so weird that every source is different on when to initiate contact.
I am of the opinion that if you want your ex back, you should go NC for a certain period of time, then IM or email them slowly, until you get back into some sort of contact with them. Then if you play it right, dinner, movies, etc, then you're back.
Some sites say wait 2 weeks, the ebooks say 30 days, enotalone says never contact them until they contact you...
It's just so frustrating that there really isn't a standard that is followed after NC. I would think logically that within a few months is the best opportunity bc your ex hasn't moved on yet in many cases, it's enough time to get over the initial anger, etc.