You're on the right track here.
What you actually need to understand is the whole idea behind exposure. It's a set of three variables, and the effects of those variables.
I'll explain this for the 4/3 system so it's not confusing - there are minor differences in depth of field (DOF) only.
Your three basic variables are:
1. Shutter Speed
2. Aperture
3. ISO Sensitivity
And the effects of those variables:
1. Shutter Speed - high speed (eg: 1/1000 s) = less light, faster exposure (less motion blur from either camera or subject movement). Low speed (eg: 1/8 s) = more light, slower exposure (lets light in over longer time; allows for or can cause motion blur from both subject and camera movement during that time!).
2. Aperture - Wide aperture (eg: f/2.8) = more light let in (allows for faster shutter speeds with less light - this is why lenses with wider apertures like f/2 are called "fast") - and causes less depth of field. Small aperture (eg: f/16) = less light (slower shutter speeds), and more depth of field. Note that DOF is increased on 4/3 because of the smaller sensor.
3. ISO Sensitivity - High ISO has the effect of allowing more light to be received on the sensor, allowing for either faster shutter speed, or narrower aperture, or both. The tradeoff is Noise.
So, all of these variables have to be manipulated based on your desired effect and the conditions of the scene. The first step is understanding what they all are used for, and what they do to the image.
The only thing that's different about 4/3 is that the basic aperture is going to be wider for the same DOF. So, as you were saying, some people recommend f/11 for general photography. This was good for film lenses, but for 4/3 and other digital SLR's, it's not necessary or optimal. On a 4/3 camera you can get that kind of depth of field at around f/8 or even f/5.6, so that's more optimal. BUT - remember that photography is all about these exposure variables, and you should change them based on what you need.
A basic idea of exposure is to focus on one variable that's important for the shot and change the others to achieve that.
For example, you generally want a fast shutter speed, around 1/(2 times the focal length) seconds, to avoid blur from camera shake (eg: for shooting at 54mm, you want at least 1/100s). You only want a slower speed if you want motion to be captured for effect, or, well, if you absolutely have to because there just isn't enough light. In that case, IS is helpful, but should not be trusted 100% - a high shutter speed is always better. To get a high speed, you have to alter some other variables - you can lower the aperture (eg: go from f/8 to f/3.5) or increase the ISO sensitivity (bump it to ISO400 or so).
For another example, say you really want everything in the scene to be in focus. So, you probably want the aperture between f/8 and f/11 (max), depending on the subject distance (someone else posted a nice table of hyperfocal distances - that's a good thing to keep in mind). So, you set your aperture, then figure out, okay, what shutter speed do I need to keep this shot sharp, and say you have 1/8s showing. Hmm, but you need it faster. So you have to increase the ISO to 800 to get up to 1/60s, which is acceptable for your focal length of say, 18mm with IS on. Then you can take the shot and are pretty much "safe." You could also compromise a little on the aperture if you don't want the noise of ISO800. Say you lower it to f/4 instead of f/8. Then you can use a much lower ISO, ISO200, and still get the same shutter speed. (math is not accurate, but that's the idea). At f/4 you might get some blur in the background, but say your subject is pretty far away, so you probably won't.
In general, you should stay away from apertures above f/11. In 4/3 they cause diffraction, which is the interference of light with itself as it passes through a hole (such as a tiny aperture). The smaller the hole, the more diffraction, and this results in a loss of sharpness in the image. However - this is an effect that is to be understood, not a hard-set rule. Sometimes you may want a small aperture to, for example, have something both 1 foot and 30 feet from the camera be in focus at the same time. The only way to achieve that may be at f/22, so the diffraction effects are a moot point, they come with the effect whether you like it or not, just like how noise comes with high ISO.
Lastly, say you want a blurred background. This prioritizes a low f-stop, since f/2 or f/3.5 (wide apertures) or so will give nice blur to the background for close subjects. This means you're letting more light in, so you're generally okay with the lowest ISO (ISO 100) and a high shutter speed (which is usually good!). Shutter speed in this case is often not a concern since the camera can do up to 1/4000s which is a pretty wide range of exposure, but in bright sunlight, often you can't shoot at f/2 because it will still overexpose at 1/4000s. You have to 'stop down' to f/4, f/5.6 just to be able to take the shot, and then you sacrifice your shallow depth of field. This is what ND filters are - they darken the image without changing aperture, allowing you to lower the shutter speed in bright situations while keeping the aperture wide.
So, safe is very relative. It's all about changing the variables of exposure for the amount of light you have and the photograph you want to capture. That's what photography is all about. There is no "magic number" for shutter speed, ISO, or aperture, even though there are guidelines. Each of them will affect the image in different ways and are all useful tools that must be understood well, both their effects and their trade offs.
Feel free to ask questions if you like! Sorry this was so long, but I hope it is helpful to someone.
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'There's nothing worse than a brilliant image of a fuzzy concept' Ansel Adams
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