An oldy but a goody;
Tool Tips are a great way to put in little notes about what fields are on a report, yet take up no space (real estate) on the report itself.
1. Right click on your object within the Crystal Designer.
2. Select "Format Field".
3. On the "Common" tab, click the "X-2" button next to "Tool Tip Text"
Now, simply insert what text you'd like to pop up by entering it in double quotes like this:
"This will be my tool tip text"
4. Now "Ok" your way back out to the designer and re-run the report.
Hover over the object you just modified and you should see your Tool Tip text.