There were lots of questions about the eyeliner and brush that I use to "tightline" my eyes, so here they are. I use blue eyeliner, and the shape of the brush is VERY important:

You need to dampen the brush with water and apply the eyeliner to the INSIDE of your lid. It's a little tricky at first, but you get the hang of it in no time. Practice makes perfect. Watch the video:

Thanks for the correct "tightlining" term Aliona, and for the video Amy.