How important is it to have keyword in meta description and alt-text?

Selected answers from the Dumb SEO Questions Facebook & G+ community.

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  Michael Martinez: The ALT= text attribute for IMG elements is intended for screen readers. It should describe what is in the image. If you can do that and still use a preferred keyword, sure, do it. But put the assisted visitor`s needs first. And if you want to know how agonzing it can be for someone who relies on a screen reader to get through a page of content, you can install a screen reader extension in your browser and let it narrate the content for you.
  
  The Meta Description tag is useful for suggesting to search engines what they can display in search results for your page. However, a page could be relevant to 1, 000 queries and you`re not going to see the same descriptive text snippet in all those queries.
  
  So you`re probably thinking about the keyword "granny smith apples" but your page is relevant to queries like "fresh fruits used in baking" and "which foods are good for your children". If you write a short meta description (which is what 99% of SEO guides and blogs tell you to do), it won`t be used for those other queries.
  
  There is no limit to how much text you can put in a meta description. The search engines will scan them for text that matches the query for which a page is returned. So if you wish you can write a 1, 000-word meta description - loading it with many descriptive phrases that are useful for a variety of queries.
  
  The content of the Meta Description tag is -NOT- used to select or rank search results. It only provides supplemental information that search engines (including site search tools) use to provide a (hopefully) helpful description of what people should expect to find if they click through to the page.
  
  6d