I suggest picking a previous project of yours that you wrote, and are very familiar with, in a different language.
Say you're familiar with Perl -- then pick a previous program of yours and try to "translate" it into C. Instantly you will have questions such as "How to accept user input in C"
Having a particular question while learning a language is the best way to memorize what you learn about it. Just reading and memorizing everything seems to be harder.
You have lot of websites to learn c programming but not all the sites they are fully transparent to teach all the concepts about c programming . Go through this following http://einstein.drexel.edu/courses/Comp_Phys/General/C_basics/ link you will be getting some idea about c programming and some basic knowledge
I have had good experiences taking classes through O'reilly.com, tho i have not taken the C courses. They are not free, but they do offer certificates, which can be useful for proving to employers that you have the skill