I'm sorry to break it to you, but (as far as I know) there is no magic tutorial or technique that is going to turn you into an expert illustrator overnight - believe me, if there were, I'd be right at the head of the queue, because my drawing skills are nonexistant! The images you have provided as examples are the product of:
(a) Years of practice and
(b) Talent.
However, there are lots of tutorials around that give you an insight into
various aspects of this kind of art - I think there are even some here at BioRUST, and many more can be found by using any Internet search engine. Here's some to get you started:
HOW TO DRAW MANGA -- MANGA UNIVERSITY
Manga Tutorials - How to Draw Anime & Manga Style
Polykarbon: Tutorials!
Anime and Manga - Learn to Draw Anime and Manga - Japanese Comics and Animation
As I said, the only thing I really know about drawing is that I can't do it, but there are some really talented members here who might be able to give you a few pointers (people like
xiaobaosg and
d31967 are two who come to mind immediately).
I don't know, but I would guess that you're quite young, so don't get disheartened - just keep practising. If you have the talent and the determination, you'll get there in the end.