"A vesicular lesion on an erythematous base is always herpes, herpes, herpes."
"Any closed collection of pus, think Staph aureus."
"Anytime you see monoarticular arthritis in a young sexually active female, gonorrhea should be the first thing on your differential."
"Fever and CVA tenderness makes the diagnosis of pyelo[nephritis]."
"You don't need to treat hot tub folliculitis; just get them out of the hot tub."
"The number-one cause of meningitis in adults is Strep pneumo[niae]."
"30% of patients with pneumonia will have a positive blood culture."
"Most ear and sinus infections are caused by The Big Three -- Strep pneumo[niae], M cat[arrhalis], and H [in]flu[enzae]."
"Folliculitis is staph, cellulitis is strep, impetigo is either/or."
Other people have songs or movie lines running through their head... I have 'Peggy's Postulates'. :) She has repeated all of those things so many times that I will remember them forever... which is simultaneously awesome and amusing.