1. One might just choose the best manuscript and edit it (copy-text method). How to choose the "best" manuscript? In order to avoid absolute subjectivism, one may choose the manuscript which is more significant within the history of the text it reproduces (e.g.: it has been used in order to teach it, is full of glosses, corrections, it has been frequently read…). The result is the edition not of the original work, but of the text as it is found embedded in a particular step of its tradition.
2. Srinivasan (see Maas 2009/10), in his 1967 edition of Vācaspatimiśra's Tattvakaumudī chose the readings to be included in the critically edited text according to a "genealogical principle": «When he finds that a reading can be taken as the genealogical starting point for changes that eventually lead to the extant variants, he adopts this reading –either an extant variant transmitted among the available witnesses, or an emendation or even a conjecture– as being the most original. The process is repeated for each and every variant of the whole text» (Maas). Obviously enough, however, there are many equivalent variants, where it is not easy to detect which one is genealogically older.