I have to agree with tommudd 100%! I wonder sometimes how many people with their hi-lift bolted down and padlocked in place even know where the keys are for it?
Don't get me wrong - I've owned and used a Hi-lift for years, and they can be quite handy, but like any tool, must be used safely. I would as a very LAST resort use only this jack to change a tire.
The safest way to change a tire is to keep the vehicle close to the ground, and lift / support it with the axle only to the point needed to get the inflated tire back on.
I don't know how many people I've seen with lifted vehicles jump out to change a flat and start cranking the Hi-lift using the front / rear bumper as the lift point.
Using the bumper increases the distance needed to go up in order to get the tire off the ground. The first 6-12 inches are needed just to uncompress the spring. Then another 6-12inches to get the tire on/off. Soon your multi-thousand pound vehicle is supported on the side you are working on by a 2-3 foot heavy-duty "pogo stick"
I've never used one, but the "sling" yellowcoyote posted looks to be about the safest way to use a hi-lift to get the tire up to where it can be properly supported by some other means. Just be careful of the body....
Eveyone should practice changing a tire in the driveway at home. This is probably the most ideal condition you will ever face, and allows you a chance to evalute the vehicles jack and the skills needed to be sucessfull. It will also bring to light any weaknesses that need to be addressed and compennsated for. Let the wife / signifigant other participate too!