Text blocks are usually arranged in various sections, subsections or subsubsections. Titles associated with these text blocks will be sequentially numbered and labeled properly by LATEX. An author must merely decide the general organization of the paper, and then permit LATEX to handle all the details including default fonts and layout.
Be careful of making too many subsections or subsubsections as this may cause a paper to seem too fragmented. Sometimes, an author will use these structures for initial organization purposes, almost as in creating an outline for the paper, but then notice that only one paragraph may be present in each subsection after the paper is actually written. In that case, it may be better to remove a bit of this excess structure and use good paragraph development to relay the same meaning. Usually, a well written topic sentence in a paragraph is sufficient to help the reader understand the content, and transition sentences from one thought to the next can assist in understanding. Therefore, it would not be necessary to have titles for subsections with ony one paragraph each, and maybe several of these sections could be grouped together with a single, more inclusive title.