How to optimize my images?

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

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  Michael Martinez: First of all, don`t overthink it. You`re still learning and it`s okay to make mistakes. Secondly, "optimization" doesn`t always work as you expect (or would prefer). Remember that everyone else is optimizing their sites, and the search engines are optimizing their algorithms, and the searchers are changing the way they search. So it`s always a moving target. Don`t ever aim for perfection. You`ll always want to improve something. THAT SAID, the "alt=" text is indeed indexed by the search engines but it`s intended to describe the image (for people who must rely on screen readers). Don`t just put keywords into the image ALT= text. Write useful descriptive sentences. Imagine what you would want to hear if you could not see the image. And you can add captions to your images where you write thoughtful comments that include the keywords you desire.
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  Chi Ip: thank you I do know we should write descriptions in a natural voice and only use keywords if they don`t sound robotic or spammy
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  Michael Martinez: Chi Ip Well, what I was trying to say (concisely) is that if you cannot use keywords to describe the image, then don`t sweat it. The ALT= text has been abused often by spammers and it`s better to not focus on keywords so much when they really don`t apply. As an illustrative example, suppose you have a product page or blog post about blue suede shoes and you include several pictures on the page, one of which is of a store front where people can buy the shoes. The ALT= text should describe the store front without mentioning "blue suede shoes"; but you could add a caption to the image that does mention them: "Customers enjoy buying blue suede shoes from our store."
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  Jim Munro: https://www.w3.org/WAI/tutorials/images/informative/
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  Ray Malaski: Matthew has training for the tool.. you should have access if you purchased it directly.
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  Perry Bernard: Equally important is deciding on the image type for the placement, and it`s bandwidth considerations. For example, if the image is placed inside a page where the maximum column width is never bigger that 780px, then sizing your image to that maximum width is all that`s ever needed. i.e. loading an image that is 2000px wide is seldom necessary unless you can make it full-screen. Consider file type too. JPG offers excellent compression to drop down file size, but it loses quality if compressed too much, or looks bad if it contains solid colours like text over plain background. JPG is best for photos, PNG needed for files that require some transparency, GIF best for images with solid plain colours. PNG almost always "looks" best, but also costs you the most in bandwidth and may cause pages to load slower than desired. While these considerations might not cost or win you too much in SEO, their effect on user experience can be dramatic and that in turn will have a flow-on effect.
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  Perry Bernard: might interest you Roberto Garcia
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  Perry Bernard: Just a little more on images within columns: You might have a desktop page that has two columns side-by-side, and each measures say 500px wide once you account for padding and margin. BUT, be aware that in mobile, it`s very likely that the duel column layout collapses into a single column at around 800px - so what I`m saying is check for max-width of a column on MOBILE if you want to decide the right width of your images. Imagine the scenario of having 4 images in a row within 2 columns on desktop, but let`s say these images are 500px, 520px, 505px and 625px wide respectively. Well, on DESKTOP these all look the same size because they squash into the 500px column, but on MOBILE they look 4 different sizes on some screens and appear messy. So to solve this, you would size your images all at 800px wide for ideal flexibility between column widths on any device.