fix the plasterboards to the ceiling joists with dry lining screws. (or galvanized nails)
bound edges of the boards go across (90 degrees) the joists.
join the boards on a joist.
stagger the joins.
900x1800mm boards are easier to fix to a ceiling, though they may not work out as efficient as say a 1200x2400mm board. it will depend upon joist spacings.
i prefer to use 12.5mm thick board.
scrim the joins and two-coat skim the lot.
you will need a hammer, a screwdriver, a sharp knife, a rule, a straight edge, a hawk, a plastering trowel, some buckets, a plasterers brush etc, etc.