Flip through tattoo magazines and look at online tattoo galleries to find different angel designs. Make a note of styles you like and dislike, so you can build an idea of the type of tattoo you would like to create.
Identify the style and meaning that the tattoo is going to have. The design could be a cherub with wings, a fallen angel with devil horns or an archangel, which has more religious connotations. The angel can represent love, religion, life or death, so it is important you know what it portrays and include these ideas in the drawing.
Assess how big the tattoo is going to be. A tattoo is completely individual, so the angel could cover the entire back or be a simple outline on the ankle. You need to know how much detail to include and what shape suits the area it is going to be drawn on.
Sketch a box that matches the size of the area where the tattoo is going to be. Use this as a frame for your drawing. If your client isn't sure of how big or small she'd like her tattoo, start at 1 or 2 inches and go from there. You can always enlarge a small drawing with a photocopier and let the client test multiple sizes to see which one she feels most comfortable with.
Sketch the wings of the angel first. The wings are a striking part of the tattoo, so positioning these at the correct angle is better than just adding them to the angel's body. Keep it simple by making them symmetrical, with a simple wing shape.
Sketch the outline of the angel's body next, before you add any detail. Experiment with the position of its body and dimensions. A tall angel will look quite different than a youthful cherub. Discuss with the client what (if anything) the angel is wearing; an angel wearing a gown, for example, might be simpler since you won't need to draw legs.
Illustrate the main features of the angel. Make sure the image is simplistic and only uses one or two colors, especially if you are a fledgling tattoo artist.