The Government announces its legislative plan at the Queens Speech during the State Opening of Parliament. For instance in December 2019, Her Majesty stated:
The Leader of the House, as Government Minister responsible for arranging the business of the House, will then issue a written statement outlining the list of legislation the Government intends to lay before Parliament during the forthcoming session
Typically, the Government tables around 30 items of legislation during each Parliamentary Session.
As per Standing Order 14(1):
Therefore, for those Parliamentary days not otherwise assigned the Government has the right to set the business agenda for Parliament. Provided sufficient notice has been given for the requisite stage, the Government can table Commons Chamber legislative stages whenever it chooses.
Government Bills must complete the same Process of a Bill as any other Bill.
Government Bills can utilise Parliamentary procedures that are not available to Private Members Bills, principally:
Programme motions set out a fixed timetable for the Bill, and are agreed following second reading. The timetable is negotiated between the party whips and states the date or time by which each stage must be completed. The motion can be amended subsequently if needed.
The House must vote to approve the Programme motion, and members may object if they feel the proposed schedule does not allow sufficient time for debate. This occurred on the 20th October 2019 for the European Union (Withdrawal Agreement) Bill, when the Government proposed just 3 days to complete all the remaining Bill stages and was rejected in a vote of 322 to 308. Without the programme motion, the Government chose not to continue with the remaining stages of the bill, and decided to call a General Election.
To ensure that debate is concluded before the end of the day, the Speaker has the power to impose a time limit on speeches made by Members, and adjust this time limit over the course of the debate. Therefore, it is not possible for an MP to filibuster (or 'talk out') a Bill as can occur for Private Members Bills
Government Bills originate from the Parliamentary Business and Legislation Committee of Cabinet which manages the Government's legislative programme on behalf of Cabinet. The Committee is chaired by the Leader of the House of Commons, and membership consists of the Chief Whips, Attorney General and the numerous Ministers for Devolved Regions.
The Committee has published an excellent Guide to Making Legislation, which provides insight into the practicalities of making the Governments legislative program into law.