To file ITR (for salaried personnel with form 16 available), two ways you can follow -
1) Online - Just keep your form 16 handy and fill all details on net itself. [read below for details].
2) Offline - Fill sahej form available at IT dept website (http://incometaxindia.gov.in/download_all.asp)& submit at nearest IT office. You can also check for ITR camps frequently organised by IT dept in month on July.
For Online ITR, again you have two ways -
1) Using IT Dept Excel sheet - offline tool to calculate your tax refund/payable. Can be used in case you have just one source or one form 16. else you have to calculate all at your own. [https://incometaxindiaefiling.gov.in/portal/downloads.do]
2) Use tax filing sites - Use diff tax filing sites, some of them are free as well. Like www.taxyogi.com
To use this site follow like -
a) Create login on this site.
b) Do fill all the details as per your form 16. In case you have more than one form 16 or form 16A, just fill one by one. It will ask for more details later, so no need to calculate anything by yourself.
c) See how much you need to pay more or get refund. In case you need to pay, fill challan 280 online and fill self assessment tax in your details as advised by site.
d) generate and mail xml file to yourself along with filled sahej form with your details. Verify details in sahej form and correct in case you find anything to be.
e) Create login on it Dept website and upload xml there [https://incometaxindiaefiling.gov.in/portal/login.do].
f) download and print IVR doc. Send it to IT office banglore.
g) heyyyyyyyy, you are done, congrats!!
