Make Lift Gate Familiarization Your Priority

The type of securement depends on the brand, model and how old your equipment is. The newest gates out there (probably the last 5-7 years) don't rely on chains anymore. They have internal locking mechanisms and the hydraulics don't tend to bleed off like they used to.
Here's a couple videos on a Maxon tuck-under that I became familiar with when I was at FedEx Freight, and the Waltco railgate that I currently use. Skip to about 3:20 on the Waltco to see how it's secured.

 

Here's a liftgate delivery technique I've used in the past when dealing with HEAVY pallets.

Like the saying goes, "Work smarter not harder" and let gravity do the work for you. If you have a customer that's on a uphill, or the pallet is just too heavy to drag, what I do is find an incline and head up nose forward. It doesn't have to be an EXTREME incline, just a slight incline will do. Drag the pallet to the tail end (make sure your're in control of your pallet on the decline) and drop it. Then get back in your truck and back the truck to a leveled surface and place the pallet on the liftgate and make your delivery. If the customer is on an uphill, drop the liftgate so it's ALMOST to the ground, but does not touch it. Get back in the truck and SLOWLY back uphill and then drop the liftgate completely to the ground to make your delivery.

Of course this all depends on if you have the right surroundings to use this method, or not making a city delivery.

 

I also carry 6 1ft lengths of 6'x2' to run the tractor up on if I need that little extra height at the front of trailer.
PS (they also make it easy to put single chains on when chaining up)

 

A place I used to work at had a couple of low-cube straight trucks with I believe it was Waltco lift gates.
I don't remember what the style is called, but you had 2 controls, up and down, and tilt, and they had pretty good tilt range.
They were the same size as the back of the truck, so they Were the door, and they were Really tough!

I used them for everything, from normal pallets to heavy carts (they had flip-up stops) to my Willys Flat fender jeep... Lol
(that was pushing it, and it was a bit scary since the back tires were slightly over the edge, but it did it! I didn't drive into the truck, because I knew getting it back to the edge was going to be tricky, but I Could have hauled it, but I was just playing that day )

It was a bit tricky, since you had full tilt control and sometimes someone would tip something off pushing the wrong button, but for loading odd things in odd places, nothing beat it.

Oh, I think it was the Waltco Level Lift.