Start off by drawing a wide m or an an upside down w.
Then draw another m under that m and add a loop through the middle part. Then begin to draw the last part but think of it as drawing a bunch of m's it'll be easier that way.
It should end up something like this. But the bottom part of mine was weird so at this point you can erase and redraw whatever lines look a bit off.
Then start to draw lines by the opening of the lip In both directions
Continue to lightly darken these lines by layering on top more lines
Do the same for the bottom but drag it out farther down
Then shade in the outer part of the lip
Go back and darken the loop you drew at the beginning.
Then shade above and below it. You'll have a very light piece in the middle.
Gently shade the lighter middle piece and then darken the darker pieces around the lip
Then there you have it a realistically drawn lip