This topic had many good tips for getting all of the glyphs: Obtaining 16 Glyphs
From this link and watching several gameplay videos about this subject I have found the following tips most useful:
- Travelers tend to show up more often in Korvax systems (but can show up in any system).
- If at a trade post in a Korvax system and a traveler is not present, try flying to orbit and back down to see if a traveler may appear. You can try this a couple of times (I have had one spawn on a 3rd visit).
- You can get another glyph from a traveler grave by marking it with a beacon and returning after doing other things. I usually visit another system and then return later, but others have shown just selling an item at the space station will do.