How to cite sources written in a different language than English? Assume one wants to cite a paper written in a different language than the article citing said paper (e.g., ones own article is written in English, but the source is French). 

How to properly handle citation in such a case?

Do I cite the original (French) title or a translated title? If I use a translated title, people might have a hard time to find the source; if the original (French) title is cited, people might have a hard time understanding it.
You cite the original title, for the very reason you gave: to enable readers to find the original title. If your work is subject to guidelines, you should also check those.

Usually, there is no point in giving a translation of the title as it does not contain any relevant information for the reader. Many citation styles do not mention the title of papers at all. I see two exceptions though:


If a translation of the cited work into English exists (but you worked with the French original), you can mention it in addition to the French title, e.g. with:


  [actual citation] (translated into English under the title [translated title])

If the title allows the reader to estimate what the source contains and whether they want to read it at all. In this case, you should arguably change your text such that it states in what way the citation is relevant for your work.