I let my truck sit for 3hrs before I did mine. It gave the line enough time to relieve the pressure in it. I have read that a few on here recommend you do it in the morning before you start the truck for the same reason. You are going to have some fuel come out of it by doing it this way so have a small bucket ready, an oil pan works great. It's doesn't splash out, it just pours out the line, not a whole lot. Or you can disable the fuel pump and run the truck until it stalls. I prefer just letting the truck set a few hrs and doing it. btw, when I finished I cycled the ignition 5 times before I started it, trying to prime the line first. When I started it I had no hick ups.

 

I have never had a problem with a lot of fuel running out. The lines pop off, I tilt them up. Some gas runs out of the filter as i twist it out of it's clamp, so i keep a rag handy. But never had a problem with fuel running out the lines.