You do not need to make an appointment at the Visa Application Center, though it is recommended to do so (it will save you time waiting for an open agent). To make an appointment at any of the 12 centers (Ahmedabad, Bangalore, Chandigarh, Chennai, Cochin, Hyderabad, Jalandhar, Kolkata, New Delhi, North Mumbai, Pune and South Mumbai) consult the "Appointment" link on the VFS website (see Resources).
Print and fill out the visa application on the UK Border Agency Visa Services website for the appropriate visa for your travels. Along with the completed application you must have both the original and a photocopy of the following documents: Indian passport with at least one blank page; proof of paid application fee; a passport-size photo; biometrics documentation and all other documents that are required for visas other than visitors (i.e. work, student, fiancée, etc.) If you do not have all of you paperwork ready and in original form it will slow the process and may end in rejection.
You must have with you at your appointment proof of having prepaid the visa application fee. The fee must be paid at a designated bank (see Resources for a list of locations). If you choose to not to prepay the application fee, you can pay at the time of your application, however there will be a surcharge. Other types of visas have variant fees, so please consult the VFS website for more details.
All Indian applicants for a UK visa must submit biometrics data in order to receive a visa. This data is collected at the time of the appointment at no extra cost to you. The biometrics are taken as a finger scan. Your fingers and thumbs on both hands will be scanned, and you should be aware that there cannot be anything on your fingers when the scans are taken. This includes henna ink or bandages. There are no exceptions. At the time of the finger scan you will also have a digital photograph taken of you, in which you must have your face completely clear of any covering, including religious attire. For more information on the biometrics exam, please refer to the "biometrics video" in Resources below.