Two recommended sources to find out how to start/change the indexing would
be Bill English's book "The Administrator's Guide to SharePoint Portal
Server 2001" and another would be the Sharepoint Portal Server Resource Kit,
available from Microsoft. These books go into great detail about the 4 ways
of indexing.
An easy way to manage the content sources is to go to Windows Explorer->My
Network Places->"workspace on server"->Management->Content Sources. Each
content source is listed, and you can modify them from there.
(right-click->properties for each one). Also, workspace-wide settings are
listed under "Additional Settings" in the same folder.
There's also a neat web part from MS for displaying content sources in a web
part, and it gives a link to the above folder. It's nice for
troubleshooting because it tells you last modified date. It's called the
Content Source Status Tool.