ST when I lost my large northern it was because the lip gripper failed.  I had never used the gripper until I had the large northern on.  My son had never used it at all either so in fairness to him that may have been the reason it didn't work.  My son had the northern by the lower lip.  When he went to pick the fish up it did not clear the side of the canoe by about 8 inches.  My son is 6' 3" and he was kneeling in the canoe.  He held the fish for a second or two and then it started to thrash and fell off.  If he had pulled the fish to the center of the canoe it would had fallen in the canoe which might of been a bad scene.  The northern was still hooked and I brought it back to the canoe, but we were unable to land it.  I think the first gripper by Berkley had a bad design.  I have purchased a second gripper and have had better luck with it.  One problem with the gripper is that it can cut a hole in the skin of the lower jaw. 
I have used the method described by Jammar and it works well in some situations.  If you are fishing with a Rapala and you try Jammar's method, your hand and the Rapala can be very close together.  The other drawback to Jammar's method is if you have to use a jaw spreader.

If you use my method correctly you do not touch the gills.  In fact you do not want to touch the gills because they are very sharp and will cut your hand up.  This may be stating the obvious, but everyone should have a jaw spreader and needle nose pliers in their tackle box.  If you don't use these you are over stressing your fish.  If you use my method correctly the fish never touches the canoe and is only touch by your hand which by the way is wet.  Dry hands are bad for fish.
The worse thing you can do is put the fish on the bottom of your canoe and then remove the lure.  Nothing good happens to a fish while it is on the bottom on your canoe.

One other thing to add.  If the lure is deep in the fish, consider cutting the line and pulling the lure through the back of the gills.  Actually cutting the line is generally a good idea and can make getting the fish off a lot easier in some situations.  Sure you have to retie, but after catching a good size northern cutting off 6 feet of line is a good idea anyways.

My method does not work as well with walleyes because of where the dorsal fin is located.  With walleyes I just grab the walleye and squeeze.  With walleyes you have to have a backward motion before you grab the fish to push the dorsal fin down.  Walleyes are much easier to grab  than northerns and trout.  On very big walleyes Jammar's method works well.
With bass grabbing the lower jaw works best.