read the script
Read the script plenty of times with an open mind, just get to know the story and the characters.
get the bigger picture
Grasp one or two words to describe the overall mood (e.g. whacky, aggressive, funny). Consider the direction you think the film is going to take stylistically. Is it a horror film, a domestic drama, a surreal film? Focus on this bigger picture. The other 'mini-moods' can fit in later.
research
Now you have an idea of mood, you need to research carefully to find the best references and inspiration. Go to the library and scour the internet; if you are not sure how to design something, find out how others did it: Ask film buff friends to recommend scenes, and view them shot by shot. Dig into your inspiration box.
consider colour
Colours are emotions. Try a muted colour scheme, such as earth colours, or whites, with occasional strong colours. These then stand out and look powerful. Colour can often underline good, evil, cool or hot-blooded characters.
st mathurin's school of practical joking
Contrasting colours emphasize contrasts between characters. Characters' clothes (colours and textures) often blend-in with their environment when they are at home. But a visitor might wear a contrasting colour. The audience does not consciously notice this, they just feel it is right.
Keep a scrap book for the main character and sets. Stick in references, colour swatches, details, etc. and work closely with these whilst preparing costume
make lists
Next make a long list of all the places and props in the script. (e.g. bicycle, bunch of flowers, sandwiches, a birthday cake, country road, sitting room, door key). Try not to forget anything. Some things will get added. Some will get crossed out. Some get a question mark.
Sometimes someone comes up with an idea you hate. Always consider their idea. Later you may realise it was complete genius
visualise
Find out what ratio the film will be shot in. Then sketch visuals to get a feel for how things could look. Think about composition, think about what shapes might be in the foreground, middleground, background. You don't have to do good drawings. Rough sketches are fine. But the mood should be as clear as possible.
Don't worry if you can't draw well. There are many ways to communicate your ideas with your team clearly. Print out photos, scribble on top, cut out stuff, stick on extra bits, draw pin men. Practically any method will do
budget & time
By now, you should have some idea about how much time and money you have at your disposal. You have to divide both up carefully because they can disappear rather quickly. For example, in a sci fi film you want a robot. There may be cheap and easy ways to make him. Do you need to buy those steel bathroom fittings to make the arms, or can you get away with insulation tube wrapped in aluminium foil? If you have people who are helping you, like a good carpenter, ask them lots of questions about how to do things and provide them with some good drawings. Keep your options open for as long as possible. (Of course, one option is to scrap the robot!) Don't make the robot just yet!
Technical drawings are very handy. You can learn the basic system in a couple of days. You do not need flashy equipment. Your drawings do not have to be engineering standard. Use tracing paper, a propelling pencil, and a transparent plastic set square and ruler
locations
You are probably not going to build a set in a studio, so you have to scout around and find good locations.
What looks good in real life is not always the same as what looks good on film. Look for bold outlines. The curve of a beach or the slope of a hill in the background. Look for higher and lower levels like steps, balconies, cellars, and ladders which mean you can use high and low angles. If safe, they can really add to the film's dynamics.
Take a tape measure and draw a rough plan. Photograph things to jog your memory later, and as a way of seeing what the camera sees. Also photograph someone at the location for scale.
Change the geography. The long shot of a house may be one particular house, the CU of the front door may be from another house. Although the hallway, the sitting room and the garden are linked in the film, they do not need to be linked in reality. If the camera does not show the wrong wallpaper through the door, nobody will ever know.
Organising a location can be a nightmare. Transport, parking, keys, access, times, other people using the space, getting in and out, permission for what you can and can't do, access, additional costs, etc. Always keep these practicalities the back of your mind. Often it means you have to scrap a potentially exciting location
adapting locations
How are you going to adapt the location? Should the space look sparse or cluttered? How you are going to dress the set? Hang up curtains? Re furniture? Bring in other furniture and props? Vary details to imply day and night.
Think about light sources. e.g. anglepoise lamps, lampshades, candlelight, parked car headlights, the camera dept will thank you for including these practical lamps
Create more visuals (see earlier) when you have an actual location.
You may not always be allowed to drill a holes in a wall. Plan alternative fixing methods
props and furniture
plain props
Don't despise boring things like tea cups and kitchen chairs. Scour junk shops and friends' living rooms. Try to get things which have real personality and are right for the character. Make simple alterations and additions as appropriate (e.g. nasty biscuits on the saucers, bright cushions for the chairs).
moving props
Look for props that move! e.g. thin net curtains moving very slightly in the breeze, a slowly rotating fan, goldfish, rustling leaves
Assume actors will need to use the furniture and pick up the props. Make sure they are stable and presentable from all angles
on set
Once filming, watch carefully. Concentrate hard. You need an eagle eye. Move the furniture and props around so that they look right. When repositioning props after camera set-up, check with the cinematographer or director. It might be positioned for a reason.
weather
Bad weather can wreak havoc. You might stand in drizzling rain all day. Are your props water and windproof? Many nice weather scenes are filmed on grotty days. During shooting there are always a few disasters. You'll do a lot of running around gaffer taping things down, or charging off to the shops to buy something. Learn to improvise!
Sometimes you find nice junk in a skip that is better than a fancy prop you spent ages making. But this is a film. This is not a sculpture exhibition. Throw away your fancy prop. Use the nice junk