ImgOps is an extremely useful meta-tool for image operations. It incorporates the following reverse/similar search services: Google, Bing, TinEye, Reddit, Yandex and Baidu. Bing, TinEye and Reddit all perform poorly in my experiences. Yandex looks promising, but I haven't tested it enough to be able to judge its strengths and weaknesses. This leaves us with Google and Baidu. For a specialized treatment on how to reverse image search using Google, please refer to this post.
Baidu's specialty lies in identifying the name of the series from anime screenshots and manga pages, and sometimes even surpasses that of Google.[case 1][case 2] Its similar images feature is also often quite accurate. It's better to pass along the unencrypted image URL (no
https in the prefix) as you might encounter this error page otherwise:
That page also shows up if you uploaded the image from local to ImgOps and followed Baidu's link from there. No worries, just click on the blue button to upload from local, or drag the image to or paste the image URL in the adjacent white box. It may be a bit tough to use Baidu Shitu (Shi-tu, not Shit-u) if you don't understand Chinese. Nevertheless, Baidu is a serious contender to Google in the reverse image search department.
I also note other resources linked to by ImgOps that might come in handy at times: anime (iqdb), anime+ (saucenao) and gif-explode. The first two are useful for finding anime wallpapers and artworks, while the last one can be used to break an animated GIF into its individual frames so you could cherry-pick the frames that will return a hit from reverse image search.
Tip: If reverse image search didn't turn in anything useful at first, wait a couple of weeks/months and try again. The (full) image could have been indexed by the search engines during this period, so you might get lucky like me and find it in your subsequent trials.
Exercise: Crop the image from this question and reverse image search with Baidu. You should get something like this:
Although the romaji is given in this case (Chou Majin Eiyuuden Wataru), you should still know how to proceed from here if it weren't given. Copy the Chinese characters enclosed in either of the red boxes added by me, and do a Google search on those characters together with the word "English". It is not clear to me if one would be able to get the name of the other series (Madou King Granzort) without knowledge of Chinese: let's leave that as a challenge.