Start by sketching shapes. I highly recommend not skipping this step because it's a guide to how your drawing will look. Don't worry about perfection on this.
Make sure you draw these shapes and lines light so they can be erased.
Using your guidelines to help you out, draw the basic sketch of Lady Gaga's body.For the joints, it helps to draw some long oval shapes and make them overlap at where the joints would be.
I know hands can be tricky but chibi hands are simple-looking so have with them. For mine, I draw a bell shape a little arc under the bottom of the bell where the joint of the fingers are.
From the "sides" of head-circle I began drawing the shape of the face. You can make a soft jaw line or one similar to this, it's up to you: http://www.dragoart.com/tuts/pics/13/10506/82819/how-to-draw-taylor-swift-step-2.png
Begin to draw her facial features; the eyes are very simple to draw. Draw two ovals that touch the lower circle-sketch from step 1. The eyelid part of the eye is a simple arch that lies above the top of that oval.
If you need more help on eyes please visit here: http://littlenubnubs.tumblr.com/post/5184950585/incase-full-size-doesnt-show-up-which-i-really
In this step we begin drawing the hair. Let the top of the head be a guide for drawing the top of her hair and let it "fall" down, so to speak. Make it look a bit flowy too, rather than stiff, if you can. :)
The bangs start right above the eyes and under the eye brows.
The bow on her head is simple if you break it down into simple shapes (though I don't think it's really needed to do this, but if you want to, go ahead), two triangles meeting up to a circle and drawing the bow shape around that.
Draw her leotard/bathing suit piece and her gloves; the gloves start at about the knuckle part of her hand. :)
Clean up the sketch, get rid of the guide lines or any messy lines that may be seen. Grab a pen or marker or make a lineart layer on your art program and begin outlining. :)
And you're done!