Your Premed Projects experience will show you what doctors do and how this impacts on the patients and other healthcare professionals. For example: a complicated case and process of determining a diagnosis can show you the uncertainties of medicine as well as helping you learn a little about the disease in itself.
Reflect and make some time to organise your thoughts whilst you are shadowing. Keeping a diary can be helpful and could also serve as a useful reminder for when you have to prepare for the application and interview. Think about what you learned, did anything surprise you, anything you particularly enjoyed about a particular department? Think about whether there were any ethical dilemmas - a question on this might well come up at interview.
Ask questions and show enthusiasm. Ask the doctors about what they think are the qualities of a good doctor, ask them about their work patterns, life-style and whether they would choose medicine again.
Be proactive and offer a pair of helping hands at every opportunity e.g. simply opening a door for patients, or offering to take a wheelchair bound patient back to the ward. This way staff will see your enthusiasm and will go out of their way to make your experience the best they can. Talk to patients - remember to be polite and and also talk to the other health professionals about their roles.