Summarized in one place, here are the rules for inserting pauses between Lojban words:
Any two words may have a pause between them; it is always illegal to pause in the middle of a word, because that breaks up the word into two words.
Every word ending in a consonant must be followed by a pause. Necessarily, all such words are cmene.
Every word beginning with a vowel must be preceded by a pause. Such words are either cmavo, fu'ivla, or cmene; all gismu and lujvo begin with consonants.
Every cmene must be preceded by a pause, unless the immediately preceding word is one of the cmavo “la”, “lai”, “la'i”, or “doi” (which is why those strings are forbidden in cmene). However, the situation triggering this rule rarely occurs.
If the last syllable of a word bears the stress, and a brivla follows, the two must be separated by a pause, to prevent confusion with the primary stress of the brivla. In this case, the first word must be either a cmavo or a cmene with unusual stress (which already ends with a pause, of course).
A cmavo of the form “Cy” must be followed by a pause unless another “Cy”-form cmavo follows.
When non-Lojban text is embedded in Lojban, it must be preceded and followed by pauses. (How to embed non-Lojban text is explained in Chapter 19.)