What are some tips, tricks, and things not to do when writing technical writing or essays?

Here are some suggestions:
Do not ramble, keep things clear and to the point. Do not say the same thing in 5 different ways. Do not write something withoutbacking it up with facts and reasons. Do not fabricate to make your writing more interesting. Do not copy others work.(duh)
Essays need to have a introduction with three mainpoints, then the next three paragraphs should derive from each point made. Then a closing paragraph summing everything up. I am not sure what technical writing means, but I am guessing it means something you would write for a paper? If thats the case then make sure you write word for word when using other peoples quotes.
I am not sure if any of this helps. It is very jumbled around, but I wrote what came to me, so I hope you get something out of it.

You don't need to have only three paragraphs of points. Just make sure every paragraph is tightly connected to one of the points you are trying to make. In university if you only have three paragraphs of points, unless they are very long and well written you wouldn't get a good mark. In high school its no problem though.
Pretty much everything else Word said is gold.
Why do you ask, if I know the circumstances, I can probably be more precise.

Three to five main points is ideal. It corresponds to the number of key items most people can grasp and remember in a single session. Threes are particularly strong, so much so that they have their owmn name - a triad.

Another recommendation is to follow your arguments in favor of your position with an acknowledgment and refutation of the strongest opposing argument, before summarizing your argument in the conclusion.

The conclusion should bring the reader's attention back to your 3-5 main points, and should not introduce any new arguments. It's purpose is to refresh the main points, so that is what your readers have in their mind when they have completed reading. For that same reason, don't remind them of the opposing position in the conclusion.

Dooviye, even in a University paper, you will probably still have three to five main points. But each point will have its own section, with 3-5 subpoints supporting each one. In the conclusion, it is the 3-5 principal points that you summarize with.

Thats what I meant, which is why I said paragraphs, not points. But I did say it poorly. Thanks for saying it a lot better then I did.

1.0 - Preamble

1.1 - In this essay I shall discuss the need to repeat each of your main points three times.

2.0 - The importance of repetition

2.1 - Repeating your points helps busy or stupid readers to understand them. All readers are busy or stupid and most are both. Therefore, repeat everything that you have to say three times: once in the preamble or foreword, once in the body text, and once in the conclusion.

3.0 - Conclusions

3.1 - From the arguments presented in this essay, you will see that your main points should be repeated three times.

Thank you all for your replies and advice.

If it helps at all, I'm thinking specifically of writing essays for college-entrance.