Well, just typing "motivation letter" or "cover letter" into Google seems to spew up links to loads of hints, tips, and how-to-s, so I guess it's not so hard to find materials outside of here.
So, instead, I'll focus on the advice that was given to me last year when I had to write one, since it worked for me :)
An important thing to realize is that a cover letter is supposed to complement your resume, not duplicate the same information. Thus, your qualifications and achievements should mostly stay in the CV.
Also, you should focus mostly on the position you are applying for, what makes you want it and what makes you think you would be good for it, which means that "how I see this technical world" probably does not deserve much elaboration (one sentence should be okay in my opinion). You are trying to convince them that you are the One and show them what makes you different from the bulk of people applying. What makes you more suited, more likely to succeed, or a better fit than other applications they're considering. (I would guess it's easier for a Master studies application since they will be admitting more than one/a handful of students).
Finally, the structure that I used, and will probably use the next time I will have to write something like that, is dividing the letter in to three parts:
you: here's where you'll put information on you. While you're not supposed to list all your achievements here, you should emphasize or elaborate on specific achievements, skills and motivations that make you especially suited for the position you're applying for
them: it is important to "prove" that you're not sending out generic application letters. You demonstrate that you're familiar with the work done in the university/lab/research group you are applying for.
If you're applying as a PhD student to a lab/professor, you might want to mention a specific paper or project and write an intelligible sentence or two about that. If you're applying for a University, you might want to pick some specific of their programme that especially caught your eye.
you and them together: first section is about how awesome you are. The second, how awesome they are. Now (to conclude), you have to show why you thing you would be awesome with them. Why do you think you're a good fit, right there? This section is not only about what they can do for you, you also have to try and convince then of how they can benefit from you.
Finally, the letter should not be longer than one page. Somewhere, you can even find this as a hard limit on an application. In my experience, you should also not have more than 3 sections. I managed to put an introductory sentence and an finishing sentence just fine in the "sections" I mentioned. Also, your writing should be impeccable. If you can, get a native English speaker to check your language. Use a spell checker. Pay attention to details. Getting an address wrong, or a letter in a name, shows sloppiness. Maybe it does not consciously affect the decision, but it might on some level.
And the last advice I got, which I did follow, but you don't have to take it as a hard rule: avoid negative statements. It's supposed to give a better tone to your letter. So, instead of saying, e.g. "Unfortunately, I couldn't find and internship during my last summer", you should write something like "Having a free summer before my last year, it allowed me to spend more time reading upon the areas of my choosing". The positive statements should help you present the facts in a more positive light.
