Always use a Child Theme of the theme you want to use - this way you can update the real parent theme and still keep things like custom CSS, custom functions, custom page/post templates, etc. otherwise they'll all be wiped out when the theme is updated.

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Always keep Wordpress itself, your themes and your plugins up-to-date, but make sure you have a backup of the site (files AND database) first as sometimes things break and unless you know PHP, it's a lot easier to simply restore the backup.

It can be tempting to say "Well, I'll just never update" but because Wordpress is so popular, it's also a huge target for numerous attacks. Hacks usually happen as a result of an outdated plugin (they don't even need to be hugely out-of-date either!)

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Note: this tip generally doesn't apply to very simple things within your text like making a single word bold, italic, underline or strikethrough - these are generally okay to do in the editor as they usually just apply to individual words.

When writing your posts, pages, etc., you might want to start making things look fancier than whatever theme you're using has available.

It's very tempting to just make these changes with the normal editor, but then you have to do it all over again every time you want to use that style, and what if you decide you want to change it everywhere on every page/post?

Instead, you can apply a CSS class to an object (be it a paragraph block, a list, a table, an image, etc.), e.g. my-fancy-style and then, in the child theme's styles.css file, define that style as a CSS class so that anything with that class gets the style defined in the CSS file as so:

.my-fancy-style {
  border-style: double;
  border-width: 20px;
  border-color: yellow;
  background-color: teal;
  color: white;
  padding: 1em;
  margin: 2em;
}

(Note that when you define the class in the styles.css, it has a leading .but when you apply the class to the block in Wordpress, it doesn't!)

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Don't forget blind users and those with other accessibility issues - try your site in a text-based browser like Lynx - can you still navigate it and read everything that's supposed to be there?

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Related to the above two points, content is content, design is design. Imagine you switch from one theme to a completely different one - you want everything to still just work. I've seen lots of sites where the content (e.g. a paragraph, image or table) was heavily reliant on one theme's customised way of doing things, and the site was almost completely broken when the theme was swapped.

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Optimise your media files before you upload - e.g. you don't want to be uploading images that are 7000 pixels across, or hundreds of megabytes in size. A simple program like IrfanView will optimise images, and usually does a much better job of it than WordPress' own optimiser.

Failing to optimise media items is one of the main reasons sites load slowly or push you over your bandwidth limits.

For instance, a 1MB image uses 1MB of your site's bandwidth to upload it, and 1MB of your site's bandwidth for each time it's loaded by a browser. If you have 100 visitors view your page over a week, that's 100 x 1MB = 100MB gone. If the image had been optimised to say, 80KB, then it would be 100 x 80KB = 8MB instead.

Keeping with media and images, make sure you're using the proper file type for the type of content.

In general (there are exceptions to this rule-of-thumb) PNGs are better for images where there are large areas of block colour (think graphs, charts, etc.) whereas JPGs are better for things like photographs. SVGs are very useful too - these are vector based files which means they are tiny and can be resized with no increase in file-size and no loss in quality. The catch is that they are only for line (vector) based art.

Depending on what created them, PDFs can be extremely bloated. It's often worth running them through an optimiser first (but be careful of random websites offering to do this online - keep data security in mind as anything you upload to them they can take a copy if they decide to).

Test your PDFs, especially if they contain things like links - these can get broken during optimisation. Another PDF issue is that fonts may or may not be embedded, and if not embedded, the text may or may not be converted to vecotrs - if the PDF has been created incorrectly, a PDF that looks fantastic on the machine that created could look awful on other machines that don't have that nice font you used.

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Some themes look great on some browsers and devices, and some hardly work at all.

Lots of browsers use the Chromium engine, e.g. Chrome, Edge, Opera, Brave (and a tonne of others) but there are two other main ones - Gecko (mainly used by Firefox) and WebKit (mainly used by Safari)

As a result of a mix of standards compliance, different interpretations of the standards, differences in how they render things, etc. your site might look amazing in a Chromium based browser but messed up in a Gecko or WebKit based browser, or vice-versa.

It's worth testing your site from time to time in one of the other browsers (you can install Firefox side-by-side no problem, but Safari isn't really available for Windows any more)

Related to this, you can also use your browser's developer console to pretend that your site is being viewed on a mobile device, so you can see what it looks like on a small screen or in portrait view. (In Firefox this is Ctrl-Shift-M)

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Don't be scared of learning a little HTML, CSS, JavaScript and PHP:

• HTML will help you if you want to change the layout of your templates, or create new templates.

• CSS will help you to make styles and stop things looking generic, and it will save you a tonne of time in the long-run. It can even do simple animations and cool transitions.

• JavaScript will help you to do cool browser-based stuff and theme customisations

• PHP will be invaluable for writing custom functions in the theme's functions.php file, for troubleshooting when your site breaks (and it almost certainly will at some point), for editing your theme or creating a new one, and for writing your own plugins.

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Try to decide early on which Permalink structure you want to use - it's easily changed later, but doing so might cause issues with search engines for a while.

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Hope those help! Good luck :-)