Approach as any GI bleed
CBC
BMP
Type and screen
Guiac
CXR
Definitive diagnosis by endoscopy
CBC
BMP
Type and screen
Guiac
CXR
Mallory-Weiss tear
Peptic ulcer disease 
Esophageal varices
Gastritis/esophagitis
Zenker's diverticulum
Gastric/esophageal varices
Achalasia
Esophageal candidiasis