Tags Tags Tags.
They help people find your work, improve you chances of being featured, and google search will love you more. So learning to do it right is a great idea.
Excessive tagging does not work in your favor. You should only use tags that are obvious keywords that would connect a searcher with your work.
Let me give you an example…
Here is an image of a calculator (courtesy of google search)
: calculator, numbers, mathematics, maths, buttons, machine, white, photograph
: calculator, numbers, integers, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, +, -, /, add, subtract, divide, mulitply, square root, screen, buttons, grey, black , white, maths, mathematics, science, finance, bookkeeping, nerd, office, administration, machine, technology, digital
Why is the second set the weaker one? Because most of the terms tagged there only have the tiniest little thing to do with the image. This then goes on to pollute the searches of people who are actually looking for an image of a + symbol or an image of a nerdy caricature . The more polluted the search is, the more times people will just give up and go elsewhere.
Anyway, hope that is some good general information for you.