The folowing tips are in no particular order.

Then filming try to shoot your subject from  different angles and at various zooms, this will give you more choice when editing your film.

When filming your subject try to get some interesting or relevant footage, say some background location shots or something related to the subject in the film. Can be used to pad out or add to your film.

When filming try to get in close to your subject, avoid using zoom if possible it tends to distort and focusing becomes a problem, your film can also suffer from camera shake, sound will be much improved as well.

When interviewing people be aware that not everyone is the same height, look for other options like sitting down or using scenes where people can be at different levels.

When interviewing people try to get the camera at the same height, this will look more natural, also remember this might not appply to creative shots.

Be aware of where your subject is when filming in relation to the sun, ideally you want the sun behind the camera, otherwise you end up with a dark shot. Avoid shooting in mid afternoon when sun is at its strongest, position your subject slightly off centre in relation to the sun may work best.

The weather can play a bit part in how your film will look, various times of the day will give different colour to your film, afternoon sunlight can give a warm look to your shot, whereas morning will look colder. Try filming at different times of day to see works what best.

Plan your filming in advance if possible, vist locations and look for suitable camera angles and wide and scenic shots, take yout time there is no rush, your film will benefit.

Shoot more footage than is needed from different angles, really helps when editing the film, gives you more options.

When editing your film only keep what you need, take anything that you feel is not needed, review your film and be very judgemental. Even if you really like a particular bit of film that is not quite up to scratch, take it out, re-do it if possible.

If you realy like a short piece of film but it has not turned out as you expected, look for more creative options like changing it to black and white, using coloured filters, blurring or distoring it. All may not be lost.

Use more than one camera to give you more options when filming, especially useful when doing interviews.

When interviewing and you only have one camera, record the interviewee answering questions first and let them get off, you can now record yourself asking the questions in the same location and edit it together later.

When filming try to get at least a minimum of 10 seconds of footage of a scene or subject, this makes editing easier, you can take it out but you cant add it in. If you plan on panning or zooming then add a little extra for a stationary shot prior to moving the camera.

How your subject will look on screen is extremely important, remember to use the rule of thirds when framing any shot, experiment in the viewfinder with your subject to see what works best.

Avoid excessive use of camera panning or zoom, try to slow the movement down depending on what your filming it will look better, control your breathing as this can have an effect on particular panning/zoom shots.

Be aware of objects that may interfere with your subject when filming, for example a big tree behind them or a street lamp. Either change camera angle or move them to a better location.

Avoid filming an interview or subject matter very close to a wall or similar, they may cast a shadow which could ruin your shot. It is always best to be a few feet away from an object or wall, and more so when doing any kind of green screen work.
  

Try to practise certain shots before you film them, especially panning or zoom shots.

When interviewing people get them to look at the interviewer and not the camera, try to always have both eyes in shot but not straight on when placing the camera and avoid profile shots makes for a better looking film, this will depend on what your filming.

When interviewing people avoid using the zoom button, instead move the camera closer, some camera zoom buttons can be awkward to control smoothly.  

Try to write down an overview of what you want to film and what you may want to include, make a list of the different camera shots, whether you want a close up, medium or wide shots. You will not be dissapointed if you can plan ahead, think about how you are going to put it all together in your mind which will make it much easier when it comes to editing.

When interviewing someone try to find out a bit more about them, give some thought to what questions you might want to ask. Don't get personal or ask awkward questions, could be end of interview.    

For some more basic help in interviewing, equipment, filming and editing your film, check out this article called How to make a Community Video using Windows Movie Maker