1. Don’t Display Comments on Protected Post – I think this one is self-explanatory. Do a check in the comments.php if you need to make a post password protected. Viewers may see the post but they will not be able to see the comments if they don’t have a password for it.
2. Display Attachments Correctly – Check the theme if you can see a special template file which is the attachment.php. It allows visitors to view your attachments correctly, like images or videos. The theme twenty ten has an attachment.php which allows viewers to see images in different sizes.
3. Introduce Right to Left Support – This one’s a bit complicated. However, you can always make this easier by checking the theme of the rtl.css that can override those in the main style.css. This is very important for languages that are Arabic as well as Hebrew.
4. Supply an Editor Style – Styling the TinyMCE editor can be easy by just creating a file named as editor-style.css. Just match the typography you see in the main style.css.
5. Make Paginated Entries Work – You can observe that paginated entries aren’t much popular in WordPress. To make it work, use the <!-nextpage-> tag. This is in order foryour visitors to see other pages beyond what they are reading.
6. Style Default Widgets – Check the widgets because more often than not, you can’t style them.
7. Make Threaded Comments Usable – make sure that comment pagination works as well as have that certain margin to know that the comment has been replied to.
8. Do Not Forget wp_footer () and wp_head () – If you leave this two out, features, headers, as well as plugins may not work.
9. Support Thumbnails – other themes rely on plugins to support thumbnails. But if you want, you can add some lines in functions.php.
10. Support Custom Menus – After registering theme support, you can display custom menu with wp_nav_menu. But remember to protect your layout to prevent weird-looking menus.
11. Enable Custom Backgrounds – WordPress 3.0 New Feature and you just got to add one line like add_custom_background(); That easy!
12. Enable Custom Headers – You can change the header background as well as the title color by defining the constants.
13. Make User-Visible String Translatable – Wrap every string users need to read with the _() if you wish to translate it.
14. Handle Custom Fields – this one’s optional for many. You will know if WordPress supports adding custom fields in each post-so check on that. You can also do this by using the function the_meta() which displays custom fields attached to a post.
15. Make sure everything looks consistent – this is self-explanatory. Make sure that comment section matches the body and the overall appearance of the site.
16. .Use the WordPress.org Theme Unit Test – WordPress.org offers a sample content file that you can import into your WordPress installation. It comes in assortment of test post, page as well as images.