For NPCs, I usually have an underlying culture in mind, and use that. When the players bump into Alfgar, Edmund, and Beorthelm, they know the culture is more-or-less Saxonish.

For PCs I usually do the same, often discussing it with the DM in advance, to find out if there are any linguistic themes I can use.

Sometimes there are hidden jokes. My elf named his horse Glorfain, which means "gold cloud" in Elvish. Only a real movie nerd will recognize Golden Cloud as the horse bought by Roy Rogers and re-named "Trigger".

And I once named two dwarven brothers, whose five brothers had been slain by a dragon, Doli and Felix. With a little linguistic knowledge, you might identify them as Grumpy and Happy.

Many of your general rules are based on assumptions about either naming practices or gaming practices that, while true in your games, are not true in others.

Quote Originally Posted by Jon_Dahl View Post
Sometimes I combine the names of the existing NPCs. For example: Tenser + Xodast = Tendast.
That's a good linguistic naming practice. The Saxons have Alfgar and Edmund, and you can make Alfmund, etc.

Quote Originally Posted by Jon_Dahl View Post
I try to use double vowels and grave/acute pitch vowels with moderation. E.g. one NPC could be "Hagár" and another "Ringaar". I always avoid ending names with double consonant because it's incredibly cheesy, like "Maxx".
Bill, Ann, Jill, Glenn, and Jeff don't seem that cheesy to me, but I understand your point. The question is what that does in that culture. Uiliacc is a perfectly good Celtic name.

And since I usually have a linguistic tradition in mind, I use diacritical marks only when appropriate. (Though I plan to name my next rogue Romeo Rascál, on the model of the OotS's Julio.)

Quote Originally Posted by Jon_Dahl View Post
I've noticed that my male characters' names usually end with "n" and female names usually end with "a". I want to help my players to differentiate the male and female NPC names. I also like names ending with "i".
Yup. That goes back to inflected languages with gender. Most Romance names ending in -a are feminine, because of the grammar rules. Note that names ending in -o are usually masculine, and Mediterranean (Mario, Julio, etc.).

Quote Originally Posted by Jon_Dahl View Post
It's very poor form to use real world names in fantasy, like "Artemis" or "Otto". It's highly unusual that a random culture with no connection to our world would have the same kinds of names that we have. All fantasy names should be different from our names, or at least not obviously taken from real life.
I disagree completely. I have no problem with a fantasy story in which the king is named Arthur, the leader is named Jason, the hero's companion is named Sam, or the giant-slayer is named David. King Arthur, Jason and the Argonauts, Lord of the Rings, and David & Goliath are the kinds of stories I'm trying to create.