Using the M-mode... how to determine settings?

Auto exposure will often be useful when the light is changing all the time, such as moving from lit to shaded places outside, or shooting under a puffy cloudy changing sky, etc. That would require adjusting the manual exposure all the time and would make the job more complicated in certain circumstances. But under certain conditions (quite often, actually), using the built-in meter will produce over- or under-exposed shots. The meter only tries to get an average amount of light in the whole frame (18%, actually) (or tries to guess what the scene is using sophisticated metering algorithms) -- but it cannot "know" what you want and decide an "intelligent" exposure. This can often be corrected using "auto exposure compensation" (that is like saying: "start from your metering, but add some more light", or saying: "your reading is not bad, but remove a bit of light from what you think"). You will learn, with experience, how to anticipate problems in a given circumstance, knowing that the camera will always try to get an averaged exposure. (For example... A person in front of a window will likely cause the auto exposure to underexpose... A winter shot filled with snow will likely cause underexposure... A pile of coal will likely overexpose... Etc.) Now, under other circunstances, you will want to use the M mode because you just don't trust the meter in your camera at all and/or you want the exposure to remain constant even when the scene changes. You may not trust your meter at all when you know a certain circumstance will have it be completely off (more than you can actually dial-in a compensation for). For example, try to take a picture of the moon at night with auto-exposure... That's a guaranteed failure. Or you may want to keep a constant exposure across many frames. I'll give you an example. Say you take pictures indoors one night with various lights, lamps, varying surface reflections, etc. You don't want your meter to ajust all the time and expose less a shot because it happens that this particular shot includes a lamp in the frame -- you likely want the exposure to remain constant for all the pictures in the series, to give a realistic representation of the place, rather than an "optimally averaged" (i.e: flat) exposure. Now, using the M mode doesn't have to be very complicated. It used to require more skill back in the film days, because every shot cost money and time. But today, the learning curve is rather steep and you can rely on good ol' "trial and error", since you can see right away what your chosen exposure did to the picture. 1- First, decide of the aperture you want. (Which aperture you would want to use would be the subject of another discussion -- it has to do mostly with what speeds you want to allow yourself, the depth of field and image quality. Quite often, you will use large apertures (small numbers) to allow all the light you can to pass, but that's obviously not always the case.) 2- Then, look what the camera suggests as a shutter speed. Set it like it tells you and take a test shot. 3- Look at the picture on your LCD (actually, it is really a better idea to evaluate the proper exposure using the histogram, and the strategy is very different when you're shooting JPEG versus raw, but we'll skip that for now :P) and see if it's good. 4- Make adjustments (fine tune) and you're set. The only difference is that once you're set, all the following shots will have the same constant exposure. I recommend, for a beginner, that you start with simpler modes at first (like "program", then probably "aperture priority", and then later "manual"), because you have plenty to learn already without having to think about that at this point. Develop the habit of looking at what apertures and shutter speeds the pictures were taken with by the auto-exposure, they will help you understand the mechanics behind the results. (Many photo browsers enable you to see the EXIF meta-data in which these details are saved.) White balance, ISO and all the other settings are not specific to the manual exposure mode, so I won't cover those here. Hope this helps...