Tickets for Melbourne public transport can be purchased on any bus or tram. The trams have vending machines which only accept coins so you must have sufficient coins to pay for your ticket. Neither buses nor trams sell the cheaper tickets.
Tickets have to be validated every time you get on a bus or tram. The first time a ticket is validated it will have it’s expiry time and date printed on it.
For a Sunday there’s a Sunday Saver ticket which allows you to go everywhere (in both zone 1 and 2) for the entire day for less than the price of a regular daily zone 1 ticket. As of the 6th of January 2008 a Sunday saver ticket costs $2.90 while a ticket for 5 days of travel in zone 1 costs $28.00 (separate daily tickets cost more).
The best value for money is the 10 * 2 hour ticket (which costs the same as a 5 * daily ticket). I have been told that if you use a multiple 2 hour ticket a second time in one day outside the 2 hour interval then it will be valid for the rest of the day. This means that a 10 * 2 hour ticket will give the same result as a 5 * daily ticket if you use it that way. If your journeys tend to be shorter then it can last for more than 5 days. Also a 2 hour ticket that is validated after some time in the evening (I believe it’s 6PM) will be valid for the rest of the night (until 3AM or whenever the transport closes down).