Ok, there have been entire books written on this subject. I'll give you some of the highlights though.
1. Normal video is recorded interlaced and at a higher frame rate than film. Film is 24 frames per second....video is 29.97 frames per second but interlaced so 59.94 fields (half frames) per second. Newer video cameras can record in progressive and at 24 frames per second to more closely emulate film...or you can use a software converter like Gramme Nattresses filters or Magic Bullet to convert your interlaced video to the 24 frames progressive 'look'. This is part of the film look as film has more 'motion blur' as moving objects move more between frames as there are fewer frames. Very simplified explanation, but the solution is to buy a camera that shoots 24P or get a NLE plug in that converts to 24P if you want this look.
2. This is MUCH more important in my eyes. Film is LIT WELL. Learn about lighting and light things well. Most films don't just blast light on a scene to get the ambient light level up....they create 'pools' of light and dark....to draw your eyes to certain areas. If you learn to light well, that will be the BIGGEST thing you can do to improve your stuff. Solution, get a book on lighting and buy a lighting kit and PRACTICE!!!!!
3. Depth of field. Most film cameras have bigger sensors and use this to 'rack' areas of the picture out of focus and focus the viewers attention and the area that is IN focus. Solution...buy a camera with bigger chips.....at least 1/2 inch. Or, use ND filters and open up your iris....move your subject away from the background, and use your focus to throw the background out of focus.
4. Camera moves. Most film has 'dolly and crane' moves that are smooth and look very good. Zooms can't emulate this as zooming is a 'flat' move that doesn't have the differentiation between foreground and background. Handholding the camera and moving with it will give you the proper 'dimensional look' but it will look shaky and crappy. Solution? Get a steadicam....a steadicam Merlin will do very nicely for smaller cameras and you can pull of the 'dolly and crane' moves with it that will look VERY smooth and professional.....as you are moving the camera through space, WITHOUT the little jiggles of handholding the camera.
Hopefully some of this helps.
Oh yeah, one more thing.
5. Don't use your video 'as is'. You can ALWAYS improve it by playing with it in your NLE. One of the things I do is to throw a 3-way color correction filter on my clips RIGHT AWAY. I usually like to increase the saturation a little. Then I throw in a 'film gamma curve.' You can 'crush' the blacks and 'pop' the whites to give it a contrasty pop. Or you can do a TON of other things with this filter....this is really one of the things Magic Bullet's and Nattress film look filters do for you without you having to know how to do this yourself....these filters convert to 24P AND do the color correction for you....and you can tweak them as well....but Color correction is a HUGE part of the 'look' of a film.
there i was thinking i could get my teeth in to this one and there goes alaskaman with his un-ending knowledge so all i can say is i agree witrh him