Hi! Mostly inspired by an amazing art piece of Temii's (Artem11s—you are required by Blackberry law to follow her), I thought I'd share my scant knowledge of the glow effect with you all. I am going to be making a sad, spooky cat in this tutorial, but this works for literally anything that glows—neon lights, phone screens, SeaWing scales—you name it.
Here is our sketch—a random character of mine that has no point except to glow and emote. Yes, it is the least symmetrical thing you'll ever see, but that doesn't matter. On with the glow!
Draw whatever you want to be glowing in a nearly white hue of the color you chose. This will be your top layer, and it will not change. Mark the edges clearly!
Duplicate the white layer twice, and put the two duplicates underneath and on alpha lock. Fill the first duplicate with a light, pretty saturated color. I'm going for a yellow-orange hue for my glow, so I selected a lighter version of that.
Go to the next duplicate and fill it with a darker, very saturated version of the color you just used. And remember—don't just go darker, move through the spectrum. If it was yellow, slide slightly into orange. If it was an aqua blue, go toward true blue. It really gives it some amazing vibrance and life.
Your layers should look like this, at this point. Remember to take the duplicates off alpha lock, or they won't blur!
Select the light yellow layer and blur it a tiny bit, just slightly past the white. You can duplicate it to brighten the effect without growing the size, which is what I did here.
Now select the orange layer and blur it so it goes a bit beyond the yellow. Duplicate it, and blur it more, so it's wider and less distinct. Your layers should look like this.
And there you have it! He's got little suns for eyes now.
Finally I'll just give him a solid body and delete the sketch layer.
There you go, and I hope that helped! Again, I'm not criticizing anyone's work, I just want to help you out! Have a great day! :D