Open a new file on Photoshop, and put a black background.
Get the Pen Tool (P) with these settings:
And create your line the way you want.
I created a line and all lines that you create using the Pen Tool appear on the Path Palette (Window > Paths). Now that we have our line/work path we are going to create another layer, go to Brush Tool (B) and select an small brush (9 px soft round). Go to the Path Palette and right click the work path you have for the line you made, and select Stroke Path.
A new window will pop up, select Brush and check Simulate Pressure. This will make the brush that you have selected to go over the line that we have. If you have a bigger brush the line will be thicker and so on, whatever color you have selected will also be showing.
This will be the result:
Now select blending options or right click the layer and select blending options. check colour overlay and give the color you want to your line.
apply Filter > Blur > Gaussian Blur
After that you should get this result.
Now that you know the basics, use your creativity to make your glow lines shine on your illustrations.