Localization/Indic
This page explains how setup your Arch installation in order to input Indic languages.
Fonts
The following packages provide fonts for a variety of Indic scripts,
See Fonts#Indic.
Locale
Setting up the locale will ensure that applications use appropriate localizations when available. Setup your locale by following instructions here.
Input methods
Since, keyboards with Indic layouts are extremely rare, you are likely to want to use transliteration. IME tools will help you accomplish this. There are several choices to try out (which allow you to use input methods especially those defined in the m17n project). The m17n project (see m17n-db, [1] [2] and [3]) provides transliteration schemes for Sanskrit, Assamese, Bengali, Burmese, Gujarati, Hindi, Kannada, Kashmiri, Maithili, Malayalam, Marathi, Nepali, Punjabi, Sindhi, Tamil, Telugu & Tibetan amongst others. So modules which allow a given IME to use m17n-db merit installation. For example, if you're installing ibus, do install ibus-m17n as well.
Localization has a good list of IMEs. The following support m17n-db input methods: