How can I develop a custom theme from scratch?
Hello World

It seems that the current version of your theme works as designed: empty templates that result in a blank screen, that's exactly what "I" would expect. Try adding "Hello Umair" in any of those empty files, and see what you get next.

Start from an example

A much more effective approach however might be as suggested by longboardnode : copy from whatever theme you like, and apply the "same-as-except"-strategy. 

Start from a base theme

Or maybe create a subtheme from your favorite base-theme (Omega, Zen, Bootstrap, ... there are plenty to pick from).

Follow the instructions in the documentation

An extremely basic example you may want to look at: Create a new custom theme with CSS alone. And if you're ready for it, study the Theming guide, especially the Theming Drupal 6 and 7 child pages of it.