Critical task in planning before getting into Tracking???

You are absolutely right if you are thinking on baseline concept.

Baseline is the snapshot of the schedule that can be used as reference point against which you may compare actual progress. It means, your original plan will be treated as baseline.

Follow the URLs to get more insight on Baseline concept

http://www.epmcentral.com/msproject/baselineintro.php

http://www.epmcentral.com/msproject/baselinesave.php

http://www.epmcentral.com/msproject/baselineview.php

or

http://office.microsoft.com/home/video.aspx?assetid=ES102776241033&width=1024&height=768&startindex=0