Criteria to optimize it for SEO:
Insert the main keywords for which your page is optimized, this will show the user that your page perfectly meets his request
Do not exceed 150 characters for the description otherwise Google will cut it
Attractiveness: The meta description must be attractive enough to make prospects want to click. The goal is to have a good "Click Through Rate" (CTR).
Things to remember:
Make sure that the description of your page is in line with the title and content of your page.
Write it in the form of a well-constructed sentence, well spelled, with punctuation.
Create absolutely unique meta descriptions to enhance your user experience.
How to set it up? (HTML Code):
The description tag should be placed after the <title> tag and before the end of header </head> tag
<head>
<title>Main keyword - value proposition + brand name</title>
<meta name="Description" content="Buy Product Name, Top Product Features + Value Proposition">
<link rel="stylesheet" type="text/css" href="MyStyle.css">
</head>
<body>
Case in point:
Case #1:
I am an e-tailer, I sell smartphones, my title should be as follows:
<meta name="Description" content="Buy iPhone 11. Dual camera with ultra wide angle. Autonomy of one day at E.Leclerc price. Home delivery or free in-store pickup">
Case N°2 :
I am an e-merchant, I sell a lot of products, I do mass import, the work must be done as follows:
Brand, model, main characteristic (everything depends on the type of product) value proposition (Free delivery or pickup, exclusive offer...) + name of the site.
Example Cdiscount :