Great answer from Richard:))

I recommend you leave them blank. If you do then search engines decide what they show.

Here's an example of the difference http://d.pr/i/ay7Y

The keyword is "afternoon tea" but I've searched for "afternoon tea at the ritz".

The first result shows Google deciding what to show from the post and emboldening my search term. The second one has a forced description so it doesn't show my search term.

I believe many people are more likely to click on a result that shows their search term in bold than one that doesn't show it at all.

It also saves wasting time and effort crafting "perfect" descriptions, especially as Google seems to be ranking higher content that doesn't have such descriptions.

However, Jay @magistudios believes that adding seo titles and descriptions results in fasting ranking, but I'd trade that any day for a higher ranking and more click throughs!

The SEO keyword meta is no longer used by search engines.