Translating in a wiki environment
If you are translating content from another wiki, consider whether you need to do a full translation or whether a partial translation or a summary is more appropriate. In some cases an adaptation may be as good as or better as a full translation and may take a lot less time.
If you are translating an article in order to introduce the article or a piece of it as new content into your wiki, you don't have to get it all done at once. Translate a few choice paragraphs, or the intro and the lede, and if you need to take a break, save and take a break. Translation, just like content creation, is a collaborative process on a wiki; take advantage of it!
It is important to keep in mind that changes in most wikis go live immediately. Although your translation need not be perfect, it is bad form to translate for speed and leave the cleanup to others, unless you check in with them first.
Unlike most commercial translation projects, there are generally no instructions provided when you sit down to translate a wiki article. If you run across something ambiguous - a specialised term that you don't know, or even something wrong in the original text - it may be difficult or impossible to track down the author(s) and get clarification from them. Certain information you would expect to see in written instructions will have to be deduced from the article itself, including: the background knowledge of the audience, appropriate style and tone, and so on.
If you are going to be working on a long article, tag it in some fashion so that others know you are working on it. If you translate slowly, that's no problem; mark a few sections as in progress and other translators can work on other sections.
The source text and the original authors must be referenced somehow from the translated content if the license of the source text requires it. Most open content licenses (the GFDL and the CC-BY licenses for example) require this. Check to see how your wiki and the source wiki handle attribution. You may be able to get by with a link to the source page and with the mention of the primary authors in the edit summary at the time you create the translated page, or special procedures may be necessary.
Wikis often do not have a mechanism in place for a translate-proof workflow. In those instances, when possible, it's good to create out-of-band mechanisms to implement a workflow. Even untranslated text gets edited and proofread by people other than the original author before being published. In your case, the content may go live immediately, but you can still work out an arrangement ahead of time for someone else to proofread shortly after you submit. This will not only improve the quality of the wiki's content but will contribute towards building of a community of translators on your wiki.
Talk to other translators on your wiki: for advice, for moral support, and for fun. Professional translators have community fora; why shouldn't the rest of us? If translation is going to be more than drudgery for you (and we hope it will be), you'll want to share the joys and quirks of it with others doing similar work.