Mostly you can use tripod to prevet the shaking but you cannot carry tripod everwhere you go.. So by using small and useful techniques you can save the day while photographing.

Praktica Revue

Here’s the useful techniques to hold your digital camera

• Hold In Both Hands – by doing this you can stabilize your camera with your body.

• Bring Your Elbows To Your Side – by doing this you will get extra stabilization. This turns your body into a kind of  tripod.

• Hold your breath while pressing the shutter -  to prevet shaking your camera hold your breath for a while.

• Look for Extra Stability – if you want to find extra stability , you can lean against a post or wall. You’ll be happy when you see how this can reduce blurry images.

Photo by Niyazi Ugur Genca

In simpler term, we define depth of field as the zone of sharpest focus in front of, behind, and around the subject on which, when lens is focused on a specific subject; with TTL (through the lens) SLR camera, DOF can be previewed in the viewfinder of a camera – the preview is very handy for critical type of work. For an example, when taking a product shot, when you require absolute certain if DOF is adequate to cover the object you intend to photograph Generally, the closer the subject to the camera, the more evenly with the distribution of depth of field in front and behind the subject. As distance of focus extends, DOF usually will be more behind than in front of the focused area.

You can use Depth of Field Calculator to understanding dept of field.

Also you can find more informtion from here or here

photo by werkunz1

Adjustment to the aperture controls the depth of field, the distance range over which objects are acceptably sharp; such adjustments generally need to be compensated by changes in the shutter speed.

By using shutter speed you can freeze action or show the passage of time in your photos.

If you want to show fast motion in your photos you have to use a fast shutter speed

If you want to show slow motion in your photos you have to use a slower shutter speed.

So you can ask what are the speed we can use in digital camres.. Here is an example of shutter speed numbers, from fast to slow:  

Piazza Ferrucci at the speed of light

1/2000 second,
1/2000 sec,
1/500 sec,
1/250 sec,
1/125 sec,
1/60 sec,
1/30 sec,
1/15 sec,
1/8 sec,
1/4 sec,
1/2 sec,
1 second.

On some digital cameras you can manually set shutter speed a lot slower than a second for very long exposures.

The focal length divided by the f-number gives the effective aperture diameter. Standard aperture settings are f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, and f/22. 

Using Aperture
1- Locate the aperture setting. Most digital cameras designate an “A” for aperture priority when the setting is adjustable. Typically, numbers should appear on the LCD, some grayed out, when in aperture mode. Aperture adjustment is typically accomplished via a wheel near the shutter button on a digital camera, which may need to be pushed. Refer to the camera’s manual if needed

2- Gain the basic understanding of the aperture function. Basically, the aperture affects how much light enters the lens to reach the camera sensor—the digital replacement for film. Aperture is essentially a hole or opening, formed by the shutter, and the aperture settings (called f/stops) measure the size of this opening. A certain amount of light is needed to properly expose a photo which is controlled by both the aperture setting and shutter speed. As expected, the larger the hole the greater amount of light that is available for exposure.

3- Familiarize yourself with the digital camera’s aperture range in the manual as it may not be available on the digital camera in different light settings. Examples include: f/2.8 to f/8.0 or f/2.0—4.8. First remember that the lowest number is a large opening (allows the most light) and the higher number is a smaller opening (allows the least light).This is opposite of what may be expected

4- Look for the f-stops between the aperture range, though memorization is not required. An example for a digital camera with an aperture of f2.8 to 8.0 may look like this: f 2.8, f 3.2, f 3.6, f 4.0, f 4.5. f 5.0, f 5.6, f 6.3, f 7.1, f 8.0. Fewer or different numbers may be seen, but these represent the measurements of the aperture or opening. Starting at f 2.8, or most light, each f/stop decreases the light by half or less. A typical digital camera set to auto mode defaults in the 3 to 5 f-stop range depending on the lighting conditions.

5- Use aperture on a digital camera to change the area of sharp focus of your photo or from sharp to blurry, otherwise known as depth-of-focus (DOF). Use the lowest f-stop (f 2.8) for a sharp foreground and blurry background, useful in portraits for example. Change the aperture to the highest setting (f 8.0) when a sharp image is desired throughout, such as in landscape photography. Take advantage of the aperture f-stops in-between to modify the amount of area where a sharp focus is desired.

6- Change the aperture setting when you need more light in a low light photo or when taking a motion shot. The first scenario works with a low f-stop, the later benefits from a higher f-stop. Advanced photography also involves adjusting the aperture and other settings to create a sharp focus of an object in motion against a blurry background.

7- Use the aperture in a digital camera to help with shaky or blurry images if needed. Many new cameras have image stabilization, and using a tripod is best, but sometimes aperture adjustment is needed. The higher the aperture, the more forgiving the digital camera is of movement