I have a Canon 1000d. Is the zone focusing technique applicable in a DSLR?
If yes, how do we do it?
If you have focus range markings for aperture settings, yes.
If you already know the possible ranges for a lens that doesn't have markings, you can use a DOF preview to see where your focal range is. IF that option isn't available to you, then you'll have to do practice shots until you understand the position on the focus ring for your best setting. If your lens does not have focus marks, then you'll really have to eyeball it!
Zone focus is a function of optics and the markings just make it easier on humans to do it faster.
The wikipedia page goes into great detail about how to read these markings: http://en.wikipedia.org/wiki/Depth_of_field#Obtaining_maximum_DOF
Edit: From the wiki article, here is the image that is used to show these marks:
On this lens the aperture is set to F11 (see the little dot above the 11 at the bottom of the image).
Just above that is a large white mark with 11's, 16's, and 22's on either side. These indicate the zone of focus for each f stop.
If your lens does not have the aperture scale with the focus marks, then you'll need to make these estimates with your eyes, noting what points are in the zone. You'll need to use your camera's depth of field preview function if available. If not, then you'll have to take a test picture and view that way.
There is an easier way to accomplish this if you don't want to look at the lens markings. Near:far distances from the same Wikipedia article cited above) are far more reliable when you are not measuring the distance to your subject. Here's how it works: There is a point we can call "optimal focus". Judged with the aperture wide open, it's pretty easy tell where that is.
Once the camera stops the lens down for exposure, there will be an area in front of and behind that point that will also be in focus. Although not strictly true for distances short of hyperfocal (again, the same article), a rule of thumb is that objects 1/3 in front and 2/3 behind are likely to be in focus. That means focus a little further away than the first object you want in focus, but not too far back because you are only likely to get 1/3 of the way.