Start off with the basic outline. (My camera doesn't want to focus today so sorry for the blurriness. I didn't realize until just now how blurry it is)
Start shading in the darkest areas with lines that are basically just N/M/W's just connected continuously. Fill the rest in lightly and feel free to add a few darker spots in the middle of the lip. I always start on the bottom lip but you can start wherever so do the same for the other lip. Blend it. This takes away any harsh lines Finally, use an eraser to create highlights.
And there we go. The tutorial on how to draw lips for @aliendestina