Make sure you do it close to an oil change. When you put the seafoam in the crankcase it will immediately start to loosen up any carbon deposits and residues in your engine, which can cause clogs and build ups at the oil filter. Put an ounce and a half (pretty sure) per quart, let it clean for the next 75-100 miles, and then do an oil change. You can use another treatment in the clean oil, and it should be good 'till the next change.
Also, I've heard that you may want to change your plugs after a seafoam treatment; not sure why, but it's something to look into anyway.
2002 Ranger XLT 4.0 4x4 & 285/75/16's
Did the "roll truck onto it's side" Mod