"Most people" means the majority of people. ie: "Most people like ice cream." I can only think of one instance where you would use "most of people". ie: "Since we all have the ability to be unpleasant, you just have to make the most of people." This is saying that you should look past the unpleasantness that is easy to see in people and look for the good which is sometimes not so easy to see. If you have seen "most of people" used in another way, please let me know. Having read Yanni's answer, I can see what you might have meant. If you put the article "the" in the phrase (most of the people) then the two phrases are similar. "Most people" would include all people everywhere. "Most of the people" usually would refer to a specific group of people. The context of the writing would identify the group. ie: "Most of the people on italki are interested in learning or teaching a language."

The precedes most when we are using superlative forms of adjectives and adverbs: the most happily married man, the most intelligent woman, etc. Here however, most = the greater number of + noun: most things are expensive, most people are kind, etc. Another way used for specific nouns, as Torsten has indicated, is most of the + noun: most of the things here are expensive, most of the people in America are kind. In any case, much will not work with countable nouns like things; it is used for uncountables: much labour is repetitive, much of the labour at our office is repetitive. .

I THINK NO DIFFERENCE BETWEEN THIS WORD THE SAME

Most people think that driving after drinking alcohol is dangerous. This means that the majority of people (in general) think this. Most of the people in this room are over thirty years old. This means the majority of the people in this room (not in general - just those people) are over thirty years old.