Keggles are great cheap brewpots and really easy to make with basic tools. There are a number of different options you can put on your keggle but i'll show you the basics.
Start out with a standard keg
You want to take a screwdriver or something firm to press on the ball to relieve pressure from the keg. You may get splashed with beer.
Once you've relieved the pressure you're going to want to remove the retaining ring that holds the spear in the keg. Find the lip in the ring and knock your screwdriver into it.
Pry along the ring and it will slowly work out of the lip.
Once you've removed the ring, you want to go ahead and turn the spear and line up the notches.
Then voila! Out comes the spear.
Next you want to verify that you have a hole or two in the rim on the top and bottom of the keg. If you don't have a hole like this(in all likelihood you will) drill one, you aren't going to hurt anything. It's sole purpose is to give it a hole to breath. There are stories of guys heating kegs and the rims exploding.
Now comes the fun part, you'll need a cutting wheel for this portion, you could probably do it with a reciprocating saw too, but wizard wheel is easiest. Take one of your homebrew buckets and throw it on the top and center it on the keg and trace. Homebrew buckets are 12" across and make a perfect sized hole. Cut your hole like so.
Make sure you grind/sand down the edges until smooth because it'll be quite sharp.
Next you'll make your hole for your ball valve/bulkhead, i chose to use a 7/8" hole saw even though a lot of the DIY's recommend a step bit. The step bit is only handy if you're making all different size holes. We're not, so a hole saw is cheaper, and easier.
Go up a few inches from the weld where the walls are straight on both sides as it will make it and easier surface to mount your bulkhead to.
Pick your desired bulkhead/ball valve combo, install it and you're ready to rock and roll
Enjoy your new keggle and brew away!