Joomla works great with templates, but sometimes you install a new template and you have to check were the new modules positions are.

Update: The options shown below are mostly specific to Joomla 1.0.x,, to find you template positions in a Joomla 1.5 installation you can use www.example.com/?tp=2

There are two way to see were each position is:

One is using the code index.php?tp=1 right after your domain URL
For example http://www.hummerbie.com/index.php?tp=1

The second one is the way I always check the postions , which is by using the function of Joomla in your administor panel that says:

Site -> Preview -> Inline with Positions

You then get a screen with all the Module positions layed out as a screen overlay with the Module numbers and names.

Once you have the positons figured out, you can start placing the modules on the positions you want them to be, moving them around until they fit your needs...