- What should be taken care of while coding a mobile theme as compared to a simple one?
- Is there any tutorial available that teaches how to develop a mobile theme from scratch?
It's really not a "wordpress" specific, it's just the css. You just give it a css for mobile browsers. That's it.
here are few good readings on how to get about the css for mobile:
if you still have some questions, feel free to ask. ;)
The best would be to use (or take a look at) Carringtion Mobile. It's developed by a known Author with lots of reputation since a long time.
You might find this series helpful is creating your own mobile theme.
A good idea would be to work a mobile stylesheet into your current theme. As one of the links added before this answer will stipulate, making your theme responsive is the way things are moving these days.