[tex-live] what to do if I want to use different paragraph separation

[Matej Kosik]

Dear all,

Normally, empty line in the *.tex file indicates that we want to start a new paragraph.
In the standard LaTeX classes (article, book, ...), a new paragraphs are indicated by indentation.

What is the best solution when, instead of indentation, I want to indicate the beginning of a new paragraph
by a vertical space in between of adjacent paragraphs?

When I try this:

	\setlength\parindent{0cm}
	\setlength\parskip{.5em}

the paragraphs are separated in the desired way,
but changing those variables affects typesetting of other elements which consequently look horrible.
- there is now a excess space between itemized list and the surrounding text
- there is now an excess space between individual elements of the itemized list.

If I want to change the paragraph separation but keep everything else unchanged, what should I do?

Somewhere on StackExchange, the advice read "you need to define your own LaTeX class".
Is this true?
If yes, didn't somebody already did this in some class?

Thanks you in advance for any tips that might help.
--
Matej