For instance, in channels about C or C++ almost everybody knows that is more efficient to multiple than divide, like: 100*0,50 in the place of 100/2 that is because processors do it faster. There is any place where a can find this kind of tips about Free Pascal ?
You asked about making the code efficient from an execution viewpoint, that is, code that runs fast. There is nothing wrong with wanting to write code that runs fast _as long as_ it is not at the detriment of maintainability (it very often is.)
When it is necessary to make code as fast as possible, first you pick the fastest algorithm, that will have a much greater effect on speed than attempting to optimize code. Once you've got the fastest/best algorithm to accomplish the goal then, you look at the assembly code the compiler generated. Sometimes you can change the source and have the compiler generate better code. Often, if you really want maximum speed, you rewrite some of the code, usually short sequences, in assembly language.
It's really important to keep in mind that optimization for speed should extremely rarely be done at the expense of maintainability. Particularly when processors are so fast. Saving 100 clock cycles on a series of instructions that doesn't get executed very often results in an imperceptible gain in time given that processors execute well over a couple billion instructions per second these days. Not mentioning that there are multiple execution units. Pick an algorithm that can be parallelized before worrying about divisions, multiplications or shifts.
C programmers are notorious for creating code that is unreadable, incomprehensible and thus unmaintainable. That's simply poor programming. The priorities when writing a program are, 1. make it correct, 2. make it easy to maintain, 3. make it readable (decently formatted and commented) 4. 1, 2 & 3 for the next 99 times and then, make it fast. Fast and good are NOT the same thing. First, make it good, then amuse yourself making it faster.
One of the best books to learn programming ever written is Oh! Pascal by Doug Cooper. You can get an older edition for just a few bucks. The book is worth its weight in gold. Not only he teaches to program in Pascal, he teaches the reader how to think in order to write good programs. Reading that book is the best thing you can do for yourself. After that pick a good book on algorithms, the second edition of Robert Sedgewick's Algorithms is my favorite because he presents the algorithms in Pascal pseudocode. After having read "oh! pascal" read a few of Per Brinch Hansen's books, those are a treat.
Hope that helps.