Tifinagh, the traditional script of the Tuareg people of the Sahara, seems not to have any established traditional ordering. However, if you organize its letters by place of articulation, an obvious pattern emerges:
This table represents Tifinagh as used at Imi-n-Taborăq in Mali, as recorded by Elghamis (2011:64-65). (Note that w is a labio-velar sound; for obvious reasons, I've chosen to place it in the velar column rather than the labial one. Also, the letter put in the laryngeal plosive slot actually just indicates the presence of a final vowel, although there are reasons to suspect that it once represented a glottal stop.) There is a lot of regional variation in Tifinagh, but one thing stands out: in every variety, everything on the right side of the thick line - ie, everything velar or further back - is consistently formed exclusively out of dots, except for g - and even that is often composed of a combination of dots and lines. Throughout much of Tuareg, original g tends to be palatalized to ǵ [ɟ], and some dialects - like this one - have lost the distinction altogether.
How this distribution emerged is unclear for the moment. It is noteworthy, however, that dot letters did not exist in Tifinagh's ancestor, Libyco-Berber as used in the pre-Roman and early Roman periods (with rare, doubtful exceptions). Two of the dot letters have clear Libyco-Berber origins; ⴾ (k, three dots in a triangle) was originally ⥤ (k, a rightwards open arrow), while : (w) was originally =. Based on these two alone, one might suppose a sort of regular form shift of = to :, in which case the development might simply be coincidental. ⵗ (ɣ) may derive from the rarely attested ÷, whose value (q?) is speculative, while ... (x) is simply a rotation of ɣ. :: (q) had no Libyco-Berber equivalent, and is perhaps historically a visual "ligature" of ɣ and + (t) - the word-final cluster *ɣt becomes qq in Tuareg. The final vowel sign · might derive from classical ☰, which had the same function; alternatively, one might derive it from or the dot occasionally used to separate words, and suppose that classical ☰ actually yielded ⵂ (h), in which case the extra dot needs to be explained.
It's not impossible that Tifinagh users at some stage made a conscious link between back consonants and dots. But even if the distribution is just a coincidence, it should still be useful for anyone seeking to memorise the script.