A lot of reception facilities will provide their own bartenders, but there are still quite a few that will not. So what do you do? There are professional bartenders out there for hire, which is a good route to go, they know how to mix drinks, and are experienced at serving large crowds.
But, if it's just not in the budget, then ask a friend; they don't often mind helping out for your wedding day. If you are planning on asking a friend to bartend your wedding, give them a list of what alcohol you will be serving that evening, and what can be done with it. It's also a good idea to create a drink menu and post it at the bar, so all of your guests can clearly see what is available to them. Also, when buying liquor at the state store for your bar, keep in mind that it's better to have more than not enough. Any unopened bottle can be returned.