Wheelock's Latin says:
In a word of two syllables the accent always falls on the first syllable: sér-vō, sáe-pe, ní-hil.
In a word of three or more syllables, the accent falls on the next to last syllable (sometimes called the "penult"), if that syllable is long: ser-vā´-re, cōn-sér-vat, for-tū´-na.
Otherwise, the accent falls on the syllable before that (the "antepenult"): mó-ne-ō, pá-tri-a, pe-cū´-ni-a, vó-lu-cris.
And regarding long syllables, it says:
A syllable is long by nature if it contains a long vowel or a diphthong; a syllable is long by position if it contains a short vowel followed by two or more consonants or by x, which is a double consonant: ks. Otherwise a syllable is short; again, the difference is rather like that between a musical half note and a quarter note.
There is an exception for the last case, as the books says:
A stop (p, b, t, d, c, g) plus a liquid (l,r) generally count as a single consonant.
Also counted as single consonants are qu and the aspirates ch, ph, th.
So, if those are the rules for accentuation, what happens when in a word, the particle -que is added? For example, the word fīlius has the accent in the antepenult: fílius, but with the particle -que, would that be filiúsque (because the syllable us would be long by position) or does the word keep its original accentuation and just adds the sound of que, thus being fíliusque?