- 1 Translator's Guide
- 2 General questions about translations
- 3 See Also
A personal opinion about translation priorities
As of June 2020, The Battle of Wesnoth official packages include 18121 strings to translate, some of them being one word only, but many are full paragraphs as well. While maintaining an existing translation might be done in a few days a year (per campaign), starting a translation from scratch will definitively be a teams work - For a new language contact Ivanovic (crazy-ivanovic AT gmx DOT net). But even single campaigns may take you down, resulting in stubs. In any case, make yourself familiar with a few technical things and procedures.
To gather a team of permanent translators is not too easy - anyhow, attracting players, that loved one campaign and want to play some more, might be a valuable approach to tease those into the team. So, a good start for your efforts might be the Tutorial and its sequel, the campaign Heir to the Throne.
You may ask - What is about the game engine, technical things, or the unit descriptions, the manual etc? Well, in my personal opinion, the campaign should go first, and perhaps the main menu buttons should be prioritized, to be able to start a game. The reason is, that in my opinion, there are more players understanding "computer English" than "story-fantasy English". With one full campaign translated, the game should attract some more translators by itself, if you put up a formal "call for help" by starting an own wiki-page for your language. If you prefer the multiplayer games over the campaigns, a different approach might be better, though.
General questions about translations
As per Lim Choon Kiat suggestion, here is a collection of problems (and solutions) for translators.
Gryphon does not exist in my language, how should I translate it?
A gryphon is a hybrid of Lion and Eagle. Hence if this word is not part of your language, then terms like "Lion-Eagle beast" are acceptable. It is important to note that this beast doesn't breathe fire. Hence, do not parallel it with a dragon or any mythical figures in your culture that breath fire.  and links to other languages will help as well.
Ogres are not known in my language
An ogre is a large, cruel, monstrous and hideous humanoid monster feeding on humans . Look out for translations of the movie "Shrek", or try to find a translation of "Perceval, the Story of the Grail" from Chrétien de Troyes (*1140-†1190) - those are told to be the first mention of the term "Ogre": "que toz li reaumes de Logres, qui ja dis fu la terre as ogres" (in English "when all the kingdom of Logres [England] which formerly was the land of the ogres").
Alternatively, parallel it with a humanoid, man-(children)-eating monsters, like the cyclops of Odysseus (unfortunately, Ogres do have two eyes) or a known fairy-tale giant. You will have to separate them from "Orcs" (those will form a gang, ogres tend not to group) and trolls (which always are related to stone and live in mountains) or Yetis (which are living in snowy mountains, but are no trolls).
How should Yeti be translated?
Yetis are white, hairy, intelligent and strong creatures living in snowy mountains and are hiding themselves. (think "white, intelligent, mystical Orang-Utan"). "snow man" or "winter beast" might be worth a try 
How should "Drakes" / "Saurians" / "Merfolk" / "Naga" / "Wose" be translated?
Noble titles and form of address
- Northern Lands - Some clarification for "Northern Rebirth" and "The Hammer of Thursagan" about "Lord Protector" and "Lord Companion" may be found here 
- Concerning diplomacy or etiquette in general
- Addressing persons as "My Lord"/"Mylady" in other languages.
Wesnoth has 2 different name generators for unit and place names, which can be adapted to your language in the wesnoth textdomain. The data that feeds them is defined in names.cfg.
The older generator simply takes a list of names, then hacks them into bits and recombines them.
The newer generator is driven by context-free grammar rules that you can define. You can find them by searching the .po file for "main=". You can test your rules on Dugi's homepage.