Most lotteries use the supported fansite - http://tibialottery.com
This is to ensure that the chosen players are really random and not something that you have impacted in any way.
Head over to TibiaLottery and create a lottery there. Make sure to remember the password so you can edit the lottery later on. Set the draw date to a date far away in the future (you will edit it later). You will also need to provide a number of available tickets (but you can edit that later too).
You also need to announce your lottery to the players - this will usually be your world board, unless you are not making a lottery for the whole world to participate (if that's the case, announce it in any other, suitable way). There are a few things that the announcement should contain:
- The number of available tickets
- The price of a ticket
- The limit on tickets one can buy (if there's a limit)
- The list of prizes (assigned to places)
- The link to the lottery (TibiaLottery generates a link for every created lottery; make sure that the post where you keep the link won't be edited - otherwise it may look as if you attempt to impact lottery results by having several lotteries set up and changing links)
- It is also a good idea to keep and update a list of tickets that have been bought and whether people have already paid for them
Once all the tickets are bought and paid for, edit the lottery and set it to be drawn in a few hours or a day. Announce the date / time of the raffle to the participants. TibiaLottery also allows you to assign ticket numbers to people, so when it's drawn it will display which player has drawn which place. Announce the winners and send the prizes!
Try to make the ticket prices fair - if you make your profit twice as big as the prizes are worth, noone might participate in your lottery.