Well, my way is simple - Tag all images (I mean use the Alt tag). Try to optimize the images in size using any online application or provider (this helps in loading them faster on the Browser) and I always mention to rename the image file something in relevance to the Text/Post or even the Keyword.
Thanks for the link you shared. It gave me the other option that I always missed out - Use of Captions.
As apart of on page optimisation Images can be a vital part of the process, from increasing user interaction, creating visual appeal and providing the images are not a hindrance there are obvious SEO benefits to be had.
How to optimise images for SEO ?
There has been a number of case studies showing that having at least one image on a page can help contribute towards better rankings. So we will start.......well at the start, prior to uploading an image to your website.
So lets get a quick overview of what we'll go through below :
Resize your images to the optimal ratio
Reduce file size for faster loading
Choose an image which is relevant to your page subject
Rename your image file name including any keywords you feel the image is naturally showing
Add a caption for easier reading
Use image alt attribute text, title attribute text if possible
Use images in your XML sitemaps
1. Image physical ratio
When selecting your image, its important especially when using large stock images or personally taken photo's that you resize your image to the aspect ratio which is going to be optimal for your site. If an the biggest image that shows on your website is 600px, then don't upload a 3000px wide image thinking that your CMS will resize and optimise the image for you. Like wise if your website is mapped out to show a 600px image, don't upload a larger one letting it scale down, upload the correct image size.
Think about your visitors, remember that although you may have a good internet connection, there is still large parts of the country and world that hasn't. Having large images that load slowly for some users create a bad user experience.
2.Optimising your image file size (after optimising the ratio)
Optimising your image for web is important, there is alot of hidden data in an image such as exif info and reducing the quality of an image to the point the human eye can not see all helps. There are of course tools to help you do this, to name a few :
My personal favourites are TinyPNG for quick optimisations and Kraken.io, Kraken because they have a great API plugin which links directly into Wordpress, optimising your images on the fly as you upload them which makes life very easy.
Can you tell the difference ? Nope I thought not.
3.Choose an image which is relevant to your page subject
Your image should always depict what you are talking about in your content body, something that will give your article visual appeal, choosing the right image will allow you to effectively name your file, title, caption and alt text.
4.Name your image file with keywords
Woah....hey there, stop right there before you run off and start stuffing keywords all over your file names, be sensible. If you've chosen an image which represents your content correctly then there should be no problem giving your file name a descriptive term of what the image is about. If you really want to get technical, use LSI keywords to diversity your reach.
5. Add a caption for easier reading
Captions again are a nice way of adding segments of text describing the image and its relation to your content, while there is no direct proof captions help with SEO, they do help with bounce rates and usability metrics. It's been said that image captions could be one of the most well-read pieces of content on your entire site.
6. Use image alt attribute text (vital),title attribute text if possible
Alt text attributes are a must if you want to succeed with optimising your images, the benefits are more than just optimising your content, but your images could also show up in Google image searches if search engines understand your image correctly.
So what are alt text and what does it do ?
Alt text is really simple, it gives an image an alternative description. If your image doesnt load on the page because a user has turned off images in their web browser or are using a screen reader due to a visual impairment then it will display the alt text instead. This is also what search engines see to best associate the image with your content and user intent.
So add your alt text to every image you add, making sure if possible that it describes the image and includes a keyword or two, again nothing wrong with adding some LSI keywords to diversity if you think you are using something to regularly.
7.Use images in your XML sitemaps
Last, but not least. Make sure your images are included in your sitemap, whether you have to use a plugin or addon for what ever CMS you are using, or if you have to hound your developer to add it to your custom script, get it done.
Hell Google says do it, so why wouldn't you ? Read this:
To give Google information about images on your site, you’ll need to add image-specific tags to a sitemap. You can use a separate sitemap to list images, or you can add image information to an existing sitemap. Use the method that works for you!