I'm very small beer (50-100 hatchlings per year) compared to some, but here are my ideas if they're helpful:
* What are the biggest problems you've encountered while breeding?
Getting the Corns to co-operate! Just because you put a male & female together, doesn't guarantee that a) they'll actually mate or b) the female will become gravid or c) the eggs laid will be fertile. I'm still waiting for a pair of 5 year olds to take any interest in each other - the male's keen but the female's having none of it. She's definitely ovulated this year, but... nada.
* For a new breeder, what is your best advice? (don't worry, i've read many articles)
Make sure that you have a market for your Corns and you'll be able to sell all that you produce. You'll be in a competitive market, dealing with large-scale breeders who have excellent reputations and can ship all over the US (I'm assuming you're in the US). I've had my fingers burned with this one.
* What corns should I breed? (I know this is a personal preference)
Definitely a personal thing (unless market research shows that the buyers you're aiming at, are looking for particular morphs). Don't buy a new and expensive morph assuming that you can breed it in three years time and make a bundle - if you've done it, chances are many others will by then as well and prices will go through the floor. Breed the ones you love, then your enthusiasm will be communicated to your customers.
* Do you use a rack system?
I don't use a rack system, but then I only have 16 adult Corns. They live in 3 or 4 foot vivs.
* Do you cool your snakes at all before breeding?
No.