Act using your natural talent, training and experience. Bring the story to life while being in character.

The Camera Operator uses the camera at the direction of the Director to capture the scenes of the film.

The Camera Assistant is responsible for focus pulling, clapperboard, handling digital media and recording shooting notes and moving equipment from one location to another.

Book: Camera Assistants Manual
Camera Assistants Manual pages at Google books

Practising - Focus Puller - Shallow depth-of-field can be used to direct the viewers eye to that which is in focus. Practice with a 35mm DSLR by manually focusing and using a low large aperture on a fast lens in live-view and move the focus point artfully bringing objects at various distances into focus over time. Use a tape measure to develop skill estimating distance.

A film without light is radio, Harry Box

Lighting work with the Director/Cinematographer to establish a look and mood.

The Boom Operator is an assistant to the sound mixer and hadles the boom and microphones to record sound during a take. The goal is to keep the boom as close as possible to the actors but out of camera frame. They also record the scene with no sound, room tone, so that it can be placed behind cuts of the audio in editing.

The Sound Mixer works with the portable audio recorder or input to the camera and makes sure audio quality is high. They also adjust the levels so that the sound doesn't overload and distort while recording as strong a signal as possible.

The On Set Dresser manages and lays out props and dress the set while considering continuity.

Hair & Makeup use the film makeup and hair kits to match the style or set the characters physical state for the scene.

The Art Department designs or build props and sets.

Fabrication: build camera cranes, car mounts, and lighting rigs.

Get an editing credits using your skill. Highend editing craft required.

Get a credit using your compositing skills. Highend compositing skills required.

Get a credit using your 3D CGI skills. Highend 3D CGI craft and Softimage, ZBrush and or Maya skills required.