1. For point and shoot digital cameras (eg GE e, x series) with an Interval Shooting function,
push Menu button on the back of your camera, go to photo:
push the right button for time lapse:
choose the interval time, push OK button, then find the timer sign on your camera, push the button:
you will find a symbol of multiple photos, choose this one:
Now the multiple photo symbol is on the display. Push the shutter release button, it will start to shoot time lapse pictures.
2. For DSLR camera with a time lapse or interval shooting mode (eg Nikon D200),
set the interval, numbers of pictures, starting time,
then you could shoot the interval pictures. I used the Aperture priority mode to shoot.
If you don't want to use the internal interval funtion, you could use an external intervalometer and 
put the plug onto your camera's external shutter release port:
3. For DSLR camera without an Interval or Time Lapse function (eg Canon XTi) but has a port for trigering the sutter by external switch, buy an Intervalometer from Aliexpress or ebay:
and put the plug onto the external shutter release port.
You have to find out which intervalometer is for your particular camera:
Definitions of DELAY, LONG (exposure time), INTVL and N on the intervalometer:
Steps for setting up the intervalometer:
To set an interval, push the SET button more than a second, you will see a bar appears under the DELAY and the first two zeros are blinking, which is the hour for delay, to set
For DELAY (this is how long your delay will be in hour, minute and second after you push the start button. To set for without delay, push the right arrow button (hour), push (minute), push (second), push:
For LONG (this is for how long your shutter will be open in hour, minute and second). To set for zero, push the right arrow button (hour), push (minute), push (second), push
For INTVL (this is the time for between two pictures in hour, minutes and second, for examply you want the interval for 3 seconds, push the right arrow button (hour), push (minute), push the up arrow three times for 3 seconds), push
For N, push the up arrow button twice for 2, push.
For the beeping sound, if you don't want to hear the sound, push up for no sound, push SET button.
After setting up, turn your camera on, then just push TIMER START/STOP button, your interval shooting will start.
