There is no required order, other than the order they are presented in, as they have nothing in common...which would be the directors' [Rodriguez & Tarantino]intent as this is specifically intended to be a homage to the low-quality/exploitation films that were usually shown in Grindhouse theatres.
Films shot for and screened at grindhouses characteristically contain large amounts of sex, violence, or bizarre subject matter. One featured genre were "roughies" or sexploitation films, a mix of sex, violence and sadism. Quality varied, but low budget production values and poor print quality were common. Critical opinions varied regarding typical grindhouse fare, but many films acquired cult following and critical praise.
A grindhouse is an American term for a theater that mainly shows exploitation films. According to historian David Church, this theater type was named after the "grind policy", a film-programming strategy dating back to the early 1920s which continuously showed films at cut-rate ticket prices that typically rose over the course of each day.
Church points out the primary definition in the Oxford English Dictionary is for a movie theater distinguished by three criteria:
Shows a variety of films, in continuous succession
Low admission fees
Films screened are frequently of poor quality or low (artistic) merit
Church states the first use of the term "grind house" was in a 1923 Variety article, which may have adopted the contemporary slang usage of "grind" to refer to the actions of barkers exhorting potential patrons to enter the venue.
Double, triple, and "all night" bills on a single admission charge often encouraged patrons to spend long periods of time in the theaters.