How do you italicize a book title when writing a source?
You can use Ctrl-I to put text in italics. For example I typed Ctrl-I before starting to write this. I can then press Ctrl-I to revert to normal text. Alternatively, if you have already typed the text normally then highlight it and press Ctrl-I.
Hope this helps.
That depends entirely on where you are "writing a source".
If you're citing a book as a source on FamilySearch's Family Tree, you can simply enter the title in the citation's Title field. The labeling of the field will take the place of any special formatting in designating the text as a title.
If you're writing a post here in Communities, you can follow Graham's instructions, or you can highlight the text and choose the capital-i icon from the popup, or you can type asterisks (*) or underlines (_) before and after the word. (The last only works as you type; if you go back and insert the punctuation, nothing happens.)
If you're writing in a plain-text environment (such as a Notes or reason field), you can indicate italics with underline characters before and after the text. (You can also use asterisks, but interpretations differ: some people use that for bold. Underlines for italics is fairly universal, going back to typewriter days.)
An exciting discovery: I found a way to make italics render in FamilySearch Family Tree (in Sources of a person's profile).
I came to this forum specifically to search for how to do this, because I spotted a title the other day that was showed up in italics--which was a fist for me--I've never seen that before.
What I can tell you, is that after a good bit of testing, the following triggers work, but ONLY for the Edit Source field labeled Where the Record Is Found (Citation). (This will not work for the Source's title field, nor will it work in the Life Sketch box--I tried both of these, as well.)
In the Where the Record is Found field, which is a plain-text environment, the triggers are as follow:
The triggers do NOT print in either the Title or the "Where the Record is Found" fields, so in the case of the Title field, the triggers just disappear but the text stays as-is. However, when I tried this in the Life Sketch field, the triggers rendered exactly as I typed them after I clicked Save (and the text of course, stayed as-is).
Just thought I would share.