From my point of view, learning by trying to use C langage may be a good way.
Even if he uses C or assemblers, he will have to learn the microcontroller architecture and he will encounter some problems with hardware. Then, he will have to investigate and so he will learn.

I've started with assembler and then with C, and I consider that learning assembler before make C more understandable, but this is my point of view and I won't tell that it's the best way. I know a lot of people who don't catch any word of assembler or microcontroller architecture and who are able to code on Electronic Control Units...

Waqar, if this could help you, I've wrote a C language rules document for embedded projects. It's surely not the best rules but this is a way to code with good tracability, reproductibility and quality.
You will find it on my website in the design rules part.

http://perso.wanadoo.fr/rs-rey/el...essources/

Regards
Stephane