Quote from fatman:
I am very active premarket and I probably make the majority of my $$$ of the positions that I start establishing in the premarket.
I can't give you a link that states the rules, but I can tell you that it is generally accepted that NYSE rules do not apply to any trades done before 9:30 or after 4:30.
Many firms have internal rules that prevent trader from establishing a short position by way of a long sale (instead of short sale). However, it is my understanding that the uptick rules do not apply to listed stocks in the pre market.