Do I need a visa?

I've been writing a series of blogs recently called top tips for first time cruisers, (you can see the full list on a tab at the top of this page, or just click the words highlighted in bold).
However it's been pointed out to me by a very nice lady on our cruise forum, that it's not only first time cruisers that need help, there are some things that all cruisers struggle with, no matter how many times they've cruised before.
One of those issues is applying for a visa.