Appointment of lead brokers etc.
Company publishes intention to float.
Institutional Roadshow (possibly)
Company issues prospectus with timetable.
Offer opens.
Offer closes.
Allocations announced.
Company apples for listing.
Stock is listed.
Dealings start in market.
Of course there are various forms of IPO like Public Offer, Intermediary Offer, Private Placing, Institutional Offer, Inst. & Retail Offer,Introduction etc.