It's pretty simple, once you know how to do it.
First of all highlight the word (makes sense):
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgGSuHKpmm_h3moTXQ7mDgbSWz3Dtsm-FYcabrxZhDw_cpKCcl5fT9KGQRp78z_Kj_ZHl0HIUsQjr5JxT6_p6u7aik2e9hRi_MAtLJ5nYjSNtKKkX1QhcQ2eoTKFObF0WRMlppU8mylK-3P/s640/1.png)
Hit the shift key and you'll see your selected word in the suggested words but with a capital letter at the beginning:
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh_rQWWcepusiV9DKbJyMRJOCWpdHieHjMwzyCVurJWY3dJbQShcL5FQClBY5EzRCw7KIS9QmILnJwalzA1QaoEiydL6TEPFIXS4oji7vpyWSuywMMC2VCv5YaADTakbpbJktyqOU0L9gu2/s640/2.png)
Double-tap the shift key to switch to capslock
Now you'll see a suggestion with the highlighted world in all uppercase:
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiEaDvziY5DQs4k2jNDe5R1O6ceeaY9YEmYqLHt02-LPSATfRYHkPnn6sE5fKk55MBj6mhLBaz67uzAR1IeZWuwYoSMEcdSL4kMgx6AwGQjIF1CVNNL2kYYoEP2TGKc6PU1VIkcWMX2dHEc/s640/3.png)
Also, if you want to switch the word to lowercase just select a word and in the QuickType suggestions you'll see the word in lowercase (when the shift key is off).
Thanks to this Reddit user who discovered this tip.