I got this asked a couple of times, so thought it best to blog it :D
The scenario in India is that we use a mix of English and Hindi words written in the Latin script. So you can easily have something like :
I am ok. Tera kya haal hai ?
The 2nd sentence is Hindi in the Latin characterset. Autocorrect is your enemy here. It will change the Hindi into gibberish. And... you only realize this after having sent the message that it totally killed it. It is quite easy to change this behavior into something that works in a better way - switch off the autocorrect :
1. Go into settings and tap on Language & Input.
2. The keyboard you use is the "Google Keyboard" it is greyed out by default as it is the default keyboard. However, the settings icon is clickable. Go there.
3. Next scroll down a bit and you will see Auto-Correction. Tap on that.
4. Turn it off.
That's it. Now you can write whatever you want, and it will not try to be too smart. The words it will think as wrong will be underlined making it easy to see the wrong spellings and what you have typed.
In case there is really an error, you can just tap that word and get a list of words that are relevant. E.g. in the above example, the ok is in small case and you can fix that by tapping as below.
That's all that there is to it. And if you really want to type in Hindi, just get the
Google Hindi Input keyboard from the Play Store and you can type it easily.