Some of the rules a text critic follows:
- old manuscripts tend to be closer to the source
- briefer texts are more probable than longer ones because a scribe is more likely to add an explanation than subtract unless they deleted a controversial passage
- bad grammar and ugly writing are more likely to be original
- the writer's style is like their fingerprint and so critics can see interpolations by others
Text critics often compile an "eclectic edition" using a collection of various source documents and then others can use that for their own work in translation. There is an eclectic edition of Greek New Testament texts called the Nestle-Aland that many modern Bible translators consult. It contains notes on variants in the source documents and why one reading or interpretation was chosen over another.