The best method is to create a batch file, write the stsadm command for taking and storing backup on some floder of your server or netwrok folder, and finaly put that on windows task scheduler.
Type Following and save as "SharepointBackschedule.bat"
echo Back up sites for the Server farm to C:\Program Files\Microsoft SQL Server\MSSQL.1\MSSQL\Backup\SharePoint\
@SET STSADM="c:\program files\common files\microsoft shared\web server extensions\12\bin\stsadm"
cd C:\Program Files\Microsoft SQL Server\MSSQL.1\MSSQL\Backup\SharePoint\
echo Directory based on the current date daytime created
%STSADM% -o backup -directory "C:\Program Files\Microsoft SQL Server\MSSQL.1\MSSQL\Backup\SharePoint\%DATE:/=_%" -backupmethod full -overwrite
Now Click on
Click on Trigger, click on New and select the schedule (Daily/Weekly etc)
Click on the Action and click on new and browse the batch file you have created.
And your scheduler is ready.