Drill bit is hollow, rimmed with diamond chip, 1/4" in size. The wood is a shim, and any thin piece of wood will do. Drill a hole in the wood with the bit.
Using an ice pick or sharp tipped anything, punch a small hole about 2" up in a sturdy plastic jug. (Little black arrow points to the hole.) This is a vinegar jug with a flip-top cap, which makes life easier.
Put some wet rags down on the surface you're going to drill on. (This is my sink, but I usually do this outside or in the basement.) When you flip up the cap, the water starts to come out of the little hole you made.
Using several pieces of board (think 2x4, 1x4, etc) build your cut off boards to the approximate height of the glass you're going to drill. (in this case, I'm using the divider between my two sinks, but usually I just have several small pieces of varying wood thickness about a foot long. That's for convenience. Place the glass on its side on top of the rags, position the shim with hole in it where you want to drill the hole on your glass. Flip cap on jug and move jug forward or back so it's getting the glass wet where you want to drill the hole. Put bit into the hole in wood at a 90 degree angle and slooowly start to drill, holding the wood shim firmly on the glass. No pressure, just let the bit do its job. After you've drilled for a very small amount of time, move the piece of wood and drill, and look for the beginning of the hole that's been etched into the glass by the drill. Put the drill back on the hole, minus the wood, 90 degree angle, and start drilling. Keep the water running over the place you're drilling. Once you get the hang of it, you can gently rock the drill bit back and forth, and it also speeds things up. Don't apply pressure on drill... let its weight do the work.
I couldn't do a picture with the drill bit inserted in the wood when drilling, because I have two hands and needed three.
Here's what the hole looks like when it's partially etched but not all the way through. The more you practice, the less etching you need before not needing to use the wood shim after you get it started.
A lot of times, opposite of what folks think, a thicker piece of glass is easier to drill than a thin one. Here's two examples of glass thickness. The one on the left was easier. Main thing is don't apply pressure. Especially with thin glass, you run the risk of shattering the glass.
Then here's a bunch I drilled in about a half hour or less. Pretty sure there were 10 or 12.
Glass all came from a thrift store, anywhere from fifty cents to around $3 for a "fancy one."
Most drills have two or three speeds. Use the lowest speed (1). I usually set the clutch setting for torque at about 4. You'll have to play with your drill to find the sweet spot, as that's a large variable between drills.
There are many ways to get there... I've been doing it for years and tweaked it many times. This is what works best for me, and is a good starting point if you're new to drilling in glass.
And OSHA reminds me to tell you always wear gloves and safety glasses when drilling.