I have done this a few times and always ended up spilling some gas. Any tricks out there to avoid this?

 

You are always going to spill a little gas.

I pulled the tank on my '02 FXD a few weeks ago to change intake manifold gaskets. I pulled the fuel line off the carb and used a piece of copper tube to extend it into a Jerry can. I also had to pull the vacuum line off the carb and keep a vacuum on it to keep the tank valve flowing. Don't take the tank valve off the tank if you don't need to because there will still be gas sloshing around in there.

 

If its your bike why don't you try one of these on the crossover..
http://quickcouplings.net/osc/index....sort=3a&page=3

probably best mod i have ever done... tank tank off in 5min..

but i'm guessing its not for your bike so i'll be interested it what comes out here..

 

I use a siphon. Much easier than fooling with fuel lines and drains more completely.