Parents are hard to convince. I gently, gently wore down the sterner of my two parents with facts, talking about how cool they are, their behavior and what they need, etc. Not pleading for one, just talking about them a little bid when the mood was light and giving a general introduction. Then the sterner parent finally pointed me to the more mellow parent. I had 'em!
Of course being a pest makes this technique self-destruct, so if you use this route you'll have to be very careful to have an incredibly light touch.
Just showing general responsibility in all areas of your life and continuing to show interest in your chosen species may also work. And save up. Even if you can't get a snake till you move out, by saving you'll get one heck of a habitat for him! 
With that said, there's a site called www.anapsid.org which has a ton of articles thoroughly covering your care questions and even the one about parents. 
-----
0.2 chickens (Falcon & Condor)
0.2 dog mutts (half ownership, only mine when they misbehave, Lucy & Amy)
0.1 Halflinger horse (Crissy)
0.0 Arizona Mountain Kingsnake (coming soon)
1.1 parents
Still searching for 1.0 WC human
