Well seeing how I do this for a living I'll throw in My $0.02 /forums/images/graemlins/whistling.gif
The best way to secure a strait axel fullsize 4x4 is to use chains on the rear axel just inside the spring mounting plates (chains with J-hooks work the best) and attach the chains to the outer corners of the trailer. On the front you want to attach to the frame not the axel. For short trips ratchet straps work fine even on a 1 ton, for long trips you should use binders. The frame will have transport slots in it where either a mini J-hook or a T-hook can be placed, then You simply run your straps or chains to the outer front corners of the trailer.
By doing this set up You compress the front springs and stretch the rear springs basicly if the rear springs tried to compress then the front springs would have to unload or vice versa so now the front and rear springs counteract each other. Also by attaching to the frame in the front you keep the heaviest part of the truck (engine) from bouncing around.
Oh and so everyone knows if you have a winch on your trailer the winch line is not a legal (or safe) for securing the vehicle. Like I said I do this everyday for a living so I kinda know what Im talking about.