When should a colon be used in the title of a manuscript?

I’m sure you have seen several papers with a colon in its title, e.g., this example I just made up:

Traffic control in a network: a new method towards X.

I’m wondering if this way of titling is recommended and what is the correct way of using colon in the title?

The format "Broad title: more specific but not sub- title" is quite commonly used. The first part is normally worded to attract the attention of a broad field while the second gives some detail of what the paper (or equivalent) is about.

There are a couple of reasons for doing this compared to an approach that would fit better in a normal sentence:

• It's likely to be shorter - the colon isn't just splicing 2 titles together but implying that one is applied to the other in some way. It's also possible to imply a stronger relationship in the title than might be strictly justifiable (by omission).
• The first part is chosen to grab the reader's attention, as some journal article titles are long enough to bore you before you've finished reading them.

Dashes are also used in a similar way (usually a spaced en-dash)

Do whatever is most prevalent in your target journal.

This is a convention of academic publishing.

For a while, two of the major competing medical journals, The Lancet and the BMJ, had different policies on title colons: one journal had colons in most of its titles; the other had colons in very few. If you submitted an article with a title containing a colon, to the wrong journal, it would seriously dent your chance of the article getting submitted.

As with all aspects of language, context is crucial.

In this case, the context is other titles in your target journal. So be consistent with them. Go through the 100 most recently-accepted published papers, and count how many have a colon in the title. If it's over 55, use a colon, if it's under 45, don't. And if it's between, do as you wish.