Have you tried just Googling 'drawing techniques'? Or searching for it in YouTube? there's a lot of free tutorials out there.
But yeah, like most people say, practice makes perfect.
If you're wanting to draw things from your mind, you need to learn how to draw the real things that they're based on. You want to draw your own characters? Practice drawing people, people sitting in the park or standing at the bus stop, people in their underwear on the internet, skinny people, fat people, women, men, people with straight hair, curly hair. Once you know how bodies work and how clothes fit, applying that to an imaginary person is much easier.
When I draw characters I still tend to get people of a similar build to pose for me and then I just fit the new skin around that structure.
If you want to draw imaginary creatures or worlds, again, draw animals, learn how they fit together and how their fur or scales hug their bodies. Draw your environment, draw plants, notice what details they have that make them look particularly plant-like.
If you're really really new to drawing, starting out by tracing photographs can be handy because it forces you to really consider every detail, which you might miss when you're trying to transfer what you're seeing over there onto a blank page in front of you.
i don said:
PS: Yes I know that this skill is one of those you have to be born with (the creative part at least)
I don't say this often but lolwut
I can't think of any part of art that a person can't pick up after being around it for enough time. Colour, composition, technique, I didn't have any of it before I started art school. It's all a matter of being exposed to it, look at other artist's work, go to exhibitions, watch videos which analyse famous art works, things will start to make sense without you even trying to learn.