Plurals seem the most common so if you see an s near your words make sure to use it! But anyway, to the crux of my solution, I have started compiling lists for the different themes I have encountered. breach, breaches, breached) (cheat, cheating) (plump, plumpish).

sometimes you can knock out 3-4 theme words just by changing the endings on them (i.e. Another key is to be thorough with the endings on your words. 'scholar' in 'scholarships' and 'weightless' in 'weightlessness'). So what I would suggest is looking for big words first because they may be the hardest to find, and then work your way down to the smaller words, especially because you can often find smaller words within the big words (i.e. Another one was 'weightlessness' for the 'outer space' theme.

For instance you for the theme of 'school' you may get 'scholarships', which takes up most of the letters on the board. It seems that for themed rounds the developers usually picked a large word that fits the theme and then the number of smaller words depends on the broadness of the theme as well as the commonality. Basically it will just take a bit of patience to find a theme that you are confident in guessing words for and there hopefully aren't too many words to actually guess. This is a difficult achievement, given that not only are some words you would think fit the theme not included (like 'chip' for 'casino' or 'fire' for 'fires'), but there are also words on there that don't seem to fit very well into the themes but are still counted at the end ('red' in 'fairy tales'). Themed rounds occur about every 6 games (theme, 2 normal, digram, 2 normal, theme) so it can take some time to actually get a themed round, let alone solve all of the words. I think this generally applies more so to digrams but you may come across this occurring in themes also.

You do not need to find the obscure words, therefore when you find an obscure themed word it will not count towards your numbers. In order to obtain this achievement, you need to find all 'common' themed words in a themed round.

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