The Majority's Habits Overrule those of the Individual - Batlah Daato Eitzel Kol Adam
General Rules
One cannot prove "normal behavior" from the acts of a shoteh : Shabbat 104b
Whether the practice of an entire country, although other countries differ in practice, still defines "popular method": Shabbat 144b; Eruvin 28a, 29b-30a
Specific Cases
In eating an olive-Sized Amount of a prohibited food abnormally: Pesachim 44a
Eating Terumah while it is connected to the ground: Menachot 70a
In determining intent for illegal transport on Shabbat : Shabbat 91a
The "normal" method of transport, as far as the laws of illegal transport on Shabbat , is defined by popular preference: Shabbat 92a-b
The method of Squeezing liquid from fruit on Shabbat is defined by popular preference: Shabbat 144b
In determining which items, when placed on the floor of a Succah Hut , become part of the floor in terms of measuring the height of that Succah Hut: Succah 4a
In determining the proper method of guarding an object : Bava Metzia 36a-b, 42a
Determining what constitutes food, vis-a-vis the laws of tumat ochlin - impurity of food : Keritot 21a-b
Determining what constitutes food, vis-a-vis the meals which merge yards for transport within on Shabbat , merge alleys for transport within on Shabbat , or extend the limit of travel outside a town on Shabbat : Eruvin 28a, 30b
Determing what constitutes "food" to require tithing : Eruvin 28a
Considering an item to be a "garment" in order to communicate impurity : Eruvin 29b-30a