Welcome to the forum
You can make something similar to this tool: http://images.oreillyauto.com/parts/...39_primary.jpg
Or you can buy it
It is inserted next to spark plug boot so you can get under it pull up the boot from underneath.
A spark plug boot is like the Chinese finger trap, if you pull on the top it will actually tighten its grip on the spark plug.
The boot puller tools are great BUT...............they often don't fit into tight spaces.
So making a few of your own, longer and short lengths, that can be used with pliers is often better.
Steel rod that can be bent without breaking but doesn't bend easily is what you want to use
Metal Coat hangers can work, but do bend a bit when pulling