I put in a medium amount of effort into writing a good title and description for my meta tags, online videos, pictures, and other online media which I want people to find. I try my best to be as descriptive as possible without being repetitive and offtopic in my descriptions.
Although, I just use around 7-10 tags, and keywords since I don't really believe keywords are very effective at making your stuff easier to find for others online since Keyword and tag spamming been such a big problem for major search engines these days, so major search engines care more about your title and description.
I agree Keywords don't matter much. I just spend 1 minute or less on them.
But, tags kind of matter since Blog search engines sometimes look at your tag and add it to their engines. plus, tags make it easier for readers and search engines to find similar content like a tag label "windows 7" will link readers to content about Windows 7 on your blog, forum, ow website.
However, you should spend sometime thinking of sentances and keywords people search for in your title, and on your content.
I saw a video on Youtube which said you should use a common phrase which people search for a lot on Google like "Saving Gas money by walking" and make sure the phrase is in your title, content, and anchor text for your link if you are writing on a Article submission website like Articlebase, Articlecity, and Ezinearticles.
I don't put much effort into the description because chances are, I will be talking about it in my post, and will be embedding the uploaded video into it. So really, no description would be necessary.