Conventions of Opening Sequences

Institutional logos are always found in films, mostly with there own intro clips. This is done to credit the institution.

Sometimes there is not the iconic clip for the institution, but simply some text stating that they are presenting the film as seen in the video below from 'Miramax Films present'. This is more often found in older films, or for less iconic institutions. The institutional logos usually appear before the film starts, but can sometimes appear after an opening clip along with the credits and title, the opening sequence in Pulp Fiction does this.

The films title is a typical convention, which can appear either after the credits or before them, but always after the institutional logos. The film title is shown to signify the start of a film.

Film opening sequences nearly always include credits of the most important actors, the director and the producer. This can draw the audience in, because they may see a famous actor they like, and also gives credit to the actors in the film.

Conventionally the main characters are introduced in the opening sequence. This is to begin the story, signifying to the audience the character's features. In some films with many main characters, not all of them can be shown in the opening sequence, but usually at least one is. Below is the James Bond clip which introduces James Bond, although this film is late in the series his features are still connoted in the clip.
Narrative Enigma is a common occurrence in opening sequences, especially within films which start in the middle of action. These questions from the audience make the film more intriguing, meaning that the audience want to watch on to find out the reason behind the enigma codes. The James Bond Skyfall opening scene has many enigma codes such as: "where is Bond?", "Who are they chasing?" and "who is the woman?".