To draw from reference in illustrator when you have a image that you want to work with, there are two approaches you can take:
Trace. You can place a layer above your photo layer (make sure your photo layer is locked) and trace directly above that with empty fill paths. You can trace precise contours and proportions this way and fill the paths later.
Reference. You can also place your photo next to your later and draw this way. Its not as precise but will allow you to use your creative juices in interpreting the photo. Using this method, guides will be helpful to help make sure proportions are correct. Use the paths with empty fills just as in the tracing method.
Regardless of the method, using reference photos along with a thorough understanding of your tools is a process of design and will help you to create wonderful illustrations with precision and creative flair.