Well, I used to have another person that always 
seemed to compete with me over Devil Hunter Yohko 
cels.  Eventually, she emailed me one day, and 
said, "please don't bid on this auction, and the 
next one that comes up that you want, tell me and 
I'll hold back."
It was the start of a cool little friendship, 
eventually we ended up telling each other about 
other cels we found but thought the other person 
would like more- 2 heads are better than one, as 
they say.  In addition, people I am friends with 
who share my interests always get first dibbs 
when I sell a cel- I usually email them privately 
before putting the cel up for general sale.