This is a reminder or memo article for me (rather than a real guide) on things I should remember, when searching for a new theme. Since it contains some not so obvious information, it can be also useful to others.
Things, you should remember about or at least consider are listed below.
Responsiveness, you fools!
A theme must be responsive! Period. For past five years (starting at 2010) there are more mobile devices sold to market each year than total number of sold desktop computers. If your theme is not responsive and is not able to adapt look and & feel even to tiniest screens, then it is no theme at all.
This blog posts includes six key points, that you should consider, when picking your WordPress theme.
Your theme must have at least one sidebar, where you will be able to put some widgets like menus, links to social or ads for monetization of your blog. This is also very important aspect, but often comes out too late.
There are many themes that supports adding a menu in one prefixed position, but has not sidebar for any other kind of widgets. These themes are also pretty worthless.
You can consider adding yourself a missing sidebar to the theme of your choice, but this requires a basic PHP skills and some basic knowledge of WordPress engine. And, your changes will be overwritten with each theme update, unless you create and use a child theme.
Thus, this solution involves a lot of work and in most cases ends up with changing theme to another one, that supports sidebar, rather than modifying current one.
Please, note, that there are many themes that has invisible sidebars -- i.e. they do not appear and do not change look & feel of your blog, if you don't put any widget onto that particular sidebar. There are, of course on contrary, many themes that has sidebar prefixed, that is visible even, when it contains no content.
For non-English blog, you must pick a theme, that supports Google Fonts or uses a font with full UTF-8 support. There is nothing worse than a blog with a font, that has non-English characters rendered in some different font.
This thing is fortunately easy to fix, because you have to only modify CSS styles, which you can easily override using Custom CSS component from Jetpack. However, drastic change of font may introduce some serious changes in general look & feel of your blog using particular theme.
It is also essential to note, that not every fontm that supports non-Latin characters, supports them on every operating system. There are many, many fonts out there, that looks perfect in your language on Windows, but fails (looks ugly) on Mac or iOS.
Thus, when picking new theme or picking new font for an existing theme, you must check it using both your desktop computer and certain number of mobile devices to make yourself sure.
Support for translations
For all non-English blogs your theme must also support translations, to have
Search etc. elements displayed correctly in your language.
Translation of theme, that is not ready for your language (or doesn't support translations at all) isn't hard.
But it -- again -- involves modification of your theme and thus forces you into creation of child theme (see above), which is usually a waste of time. Picking theme, that supports translation or ignoring the fact, that certain parts of theme are not translated, is usually a better option.
Featured images, photos etc.
Picture is worth a thousand words! If you don't post something with an image, you have a big chances, it won't be noticed.
Remember about this and try to always pick theme, that supports featured image to each post and page (at least). Also consider enriching your post texts with a reasonable number of photos, diagrams, images, screenshots etc.
The "read more" thing
Last, but not least. Small thing, but may be annoying for many people.
Many themes ignores
<!-- more --> more tags and you loose control on where post's introduction ends. These themes cuts introduction where they like and this may produce unwanted final effect. Check, if you perfect theme respects, that you are the actual content author and thus that you (not theme) controls, where, what ends or starts.
Even if you're using a pure English blog and don't need things like sidebars, you can consider above checklist to initially filter themes, when you're looking for a new one. It is always better to have more professional and flexible theme, supporting many obvious features, even if you don't plan to use them initially.