My process:
>choose categories
>upload photos
>Using a template that I devised on Excel, list tags (where I get the tags explained below)
>rearrange tags as needed
>Using a blank Notebook page, write the title, with commas - using all the tags
>Here’s where I proof-read the title for typo’s
>Cut and paste the title, delete the phrases at the end until title is within 140 characters
>Write the description (a lot of the description I have previously written in a word file, those are cut and pasted into the listing)
>Cut and paste the title from the Notebook page into the tags box. (As mentioned, the software rejects tags that are >20 characters or are otherwise not correct)
>Tweak the tags as needed
>Complete the listing.
>Save the tag list in Excel for later use.
Where do I get tags:
> study my stats to see the most frequent phrases over the last few months
>I look at the tags of the competition - from the search pages 1,2,3. I type in a search phrase and see what tags the other sellers use.
>Also I type in a generic phrase, like baby blanket, and see what suggestions show up below the search box, then search those.
>Sometimes I use Google Analytics, not often enough.
I developed this process over the last year, it seems to be working for me. Hope it helps.