That's like asking how long a piece of string you need to put between two trees in your garden to make a washing line. Without knowing how far apart the trees are it's imppossible to say.
Similarly with your question, without knowing what it is that you are trying to take pictures of it's difficult to give specific advice.
Going to basics, there are 3 elements to worry about in the picture taking process:
Shutter speed
Aperture
ISO
Choice of shutter speed is usually governed by how much blur you want to record, or how fast something is moving. If you want to freeze any movement you will need a fast shutter speed. If you want to show movement and introduce some blur then you will need a slower speed.
Aperture governs something called depth of field, which is basically how far in front and behind your point of focus remains acceptably sharp. A small aperture (big number) has a greater depth of field. A big aperture (small number) has a shallower depth of field and is useful for seperating your subject from the background where you can keep the subject sharp and blur the background.
Given the above you would think that to get the sharpest pictures all you need to do is use a fast shutter speed to freeze any movement and a small aperture to get a large depth of field. The problem here is that both options are tending towards not letting much light through to the sensor, and both together may not allow enough light to give a correct exposure resulting in a dark image.
A possible solution is with the 3rd variable, ISO. Low ISO means that your sensor is less sensitive to light, so will need more light from your choice of shutter speed and/or aperture. A high ISO setting means that your sensor is more sensitive to light, and can work with less. This sounds like the solution to using combinations of fast shutter speeds and small apertures, but there is a downside. High ISO results in noise in your image and can be quite bad at reallly high settings.
So, as you have probably realised, it's all a bit of a juggling act and it often depends on how bright your scene is as to what particular settings you can use.
To start with I would suggest using the camera in Av or Tv mode. In Av choose an aperture that is one or two settings away from wide open i.e. if your lens has a maximum of 2.8 try using 4 or 5.6. Set the ISO to 200, and your camera will then select a shutter speed to give the right exposure. If that shutter speed is a bit slow and you are working in poor light, the result may show signs of blurring. If that is the case you can select a slighter higher ISO setting and/or open the aperture a bit wider.
If using Tv mode the general rule of thumb is to not go lower than 1/focal length so if you are using a 50mm lens, don't select a shutter speed slower than 1/60. Again select ISO 200 and the camera will choose an aperture to match. Again if the lighting is a bit dim, if you are shooting indoors for example, your lens may not be able to open wide enough to allow enough light in to give a correct exposure, so you will need to either increase the ISO setting, or select a slower shutter speed and run the risk of recording movement blur.
HTH.
. One way I found of learning what settings worked best for different things I was photographing was to take the same pic but try different settings, you can then see the difference between them. Also dont forget to change your ISO depending on the lighting you have. Im still very much a novice but have learnt so much just through trial and error 
