Every one can communicate best in their native language. In earlier days special fonts are necessary to write in native languages. These days because of unicode support we can write in almost all indian languages in desktop applications like MS word, notepad and at the same time in web applications and in social networking sites like twitter, facebook, buzz.
Presently indian languages like Kannada, Konkani, Tulu, Hindi, Marathi, Sanskrit, Tamil, Telugu, Malayalam, Gujarati, Punjabi, Bengali, Assamese and Oriya have unicode support. ( Let me know if I miss any language).
Write telugu in Facebook ( Quick Method )
There are many a ways to type telugu in Facebook. If you want to write a quick text in Facebook you can use tool http://epalaka.com
Go to http://epalaka.com and there you can easily write telugu using english spellings and click facebook share button as shown in the below figure.

and your content is easily shared in Facebook.
Method II using Google Indic transliteration
As I am huge fan of Google, I use Google Indic Transliteration IME a tool developed by Google. Let us see how to use Google Indic Transliteration IME version
Download your language Google Indic Transliteration IME specifiying 32bit or 64bit
Install in your system.
How to turn on ?
Language bar will set turned on automatically in your task bar. Click in ‘EN’ and select your language.

How to type a document.
After turning it on, Using your normal keyboards, just type the required text as it sounds and this transliteration converts it into native text. It also provides predictions. The text generated is in unicode. Once tool is downloaded there is no depency over internet.

So as use this tool in online application like facebook, twitter, turn on the google indic and simply follow how you type in word document.

Though they are lot of tools that can help to generate indian languge native text. I prefer to use Google Indic Transliteration IME which helps to generate native text along with predictions.
Currently Google indic supports 22 languages.
If you dont want to download and use, you can use ePalaka an alternate tool to generate telugu so easily online and it is free