rules and procedures

if you are sales under 20Lakh u don't need to register under Gst.

but u have option to take Gst registarion as a regular delear

24. Compulsory registration in certain cases (1) Notwithstanding anything contained in sub-section (1) of section 22, the following categories of persons shall be required to be registered under this Act, –– (i) persons making any inter-State taxable supply; (ii) (iii) (iv) (v) (vi) (vii) (viii) (ix) (x) (xi) (xii) casual taxable persons making taxable supply; persons who are required to pay tax under reverse charge; person who are required to pay tax under sub-section (5) of section 9; non-resident taxable persons making taxable supply; persons who are required to deduct tax under section 51, whether or not separately registered under this Act; persons who make taxable supply of goods or services or both on behalf of other taxable persons whether as an agent or otherwise; Input Service Distributor, whether or not separately registered under this Act; persons who supply goods or services or both, other than supplies specified under sub-section (5) of section 9, through such electronic commerce operator who is required to collect tax at source under section 52; every electronic commerce operator; every person supplying online information and database access or retrieval services from a place outside India to a person in India, other than a registered person; and such other person or class of persons as may be notified by the Government on the recommendations of the Council.

if u fall in these category u have to take compulsory registration

so who to make bill

should I have to collect tax on my sales or not

If u r falling in GST category than refer chapter vii (section 31 -34) ..if u r not registered make the bill as u were making it before..

Registered dealer issue Tax invoice
Unregistered and composition dealer issues bill of supply

@ sandeep unregistered dealer are not required to issue bill of supply..they can issue any format they want to..if u have read it anywhere please provide the section number.

Ok agree with Ankit
a registered supplier needs to issue bill of supply:

1 Supply of exempted goods or services
2 Supplier is paying tax under composition scheme