This series of articles, "The Rational Clinical Examination" in JAMA is by far one of my favorite approaches to medicine. They ask simple clinical questions, and they do literature searches to find evidence to apply. Additionally, the form in which they distill the evidence tends to be likelihood ratios - a far more useful statistical construct in estimating how a particular finding contributes to ruling-in or ruling-out disease.
This most recent literature review covers gastrointestinal bleeding - and it covers a few worthwhile points. Most encouragingly, the authors are exceedingly skeptical about the utility of NG tube placement - reasonable positive LR for UGIB, but, as the authors note, a suspected source is usually well-established prior to NG tube placement. Additionally, they note that the NG lavage does not tend to influence final patient-oriented outcomes - and lean towards not recommending its use. Secondly, they also cover the Blatchford and Rockall scores, which are decision instruments that might have value in helping triage patients for outpatient management.
"Does This Patient Have a Severe Upper Gastrointestinal Bleed?"