Like many other programs CamStudio works very well without changing any settings, but you may want to tweak some things to your liking though.
Main window in CamStudio
One of the things that you may want to change is to capture the whole screen or just a portion of the screen. To do this all you will need to do is go to Region > Region, Fixed Region, or Full Screen. When you select Fixed region you can choose the size of the space that you would like to record.
Region options menu
Another important option that you may want to change is where the videos are going to be saved. You can change this by navigating to Options >Program Options > Temporary Directory For Recording > Use Windows Temporary Directory, Use Installed Directory, or Use User Specified Directory. To change it to a directory that you choose on your own you will need to select Use User Specified Directory.
Changing the directory where video is saved
One more thing that would be more common for recording games and such would be to not show the cursor while recording. This can be done by going to Options > Cursor Options. You can then select whether the cursor is shown or not by selecting the corresponding button.
These are just some of the main features that you may want to play around with but there are still a ton more options that I have not shown too. So if you would like a very strait forward program to do some screen captures CamStudio is a very good choice. Have fun making some screen captures. If you would like to share some that you have made with me feel free to upload them to youtube or similar and then post a link in the comments or you can send a link to my email @ firstname.lastname@example.org