SQLite is a single-file database which follows the zero-configuration approach. It is furthermore easy to use and is thus perfect for your first experiments with liquibase.
There is a jdbc driver available here: http://www.zentus.com/sqlitejdbc/
To use sqlite with liquibase you will need the following information:
jars for the classpath: * sqlitejdbc-v<version>.jar
jdbc driver name: * org.sqlite.JDBC
jdbc url: * jdbc:sqlite:<database-name>
There is no need to create a database before you can use sqlite, as I said: it follows the zero-configuration approach.
A run of liquibase with sqlite, having the sqlite.jar and the in the current directory (and the liquibase.jar at hand as well), could look like this:
Tip: There is an easy to use firefox extension which can be used to display and edit a sqlite database. Find it over here: https://addons.mozilla.org/de/firefox/addon/sqlite-manager/
Have fun :)