Do not use the * selector as that will apply to all elements on the page. Suppose you have a structure like this:
...
<body>
<div id="content">
<b>This is the main container.</b>
</div>
</body>
</html>
You can then center the #content div using:
#content {
width: 400px;
margin: 0 auto;
background-color: #66ffff;
}
Don't know what you've seen elsewhere but this is the way to go. The * { margin: 0; padding: 0; } snippet you've seen is for resetting browser's default definitions for all browsers to make your site behave similarly on all browsers, this has nothing to do with centering the main container.
Most browsers apply a default margin and padding to some elements which usually isn't consistent with other browsers' implementations. This is why it is often considered smart to use this kind of 'resetting'. The reset snippet you presented is the most simplest of reset stylesheets, you can read more about the subject here: