Make an alias of Mac CallerID and put it in "Startup Items" folder inside the system folder. This way every time you startup Mac CallerID will be ready to receive calls.
Using another Communication program
Mac CallerID should surrender the serial port when you use another communications program and force the port open. When you quit the other application, Mac CallerID should automatically reinitialize the port. You do not need to hit the "Initialize..." button.
If you have problems, try using the AppleScripts to release and init the serial ports (available only to registered users).
Background
Set the preferences to hide or shrink the window when in the background. After Mac CallerID has started up, simply click outside the window and it will either shrink or hide.
If Mac CallerID is in the background, you can set the "Bring Window" to front preference to have Mac CallerID come to the front when a new call comes in.
After a new call comes in click on the flashing indicator to stop the flashing. The indicator will also stop flashing when you dial a number or change the display from single call to the call list.
If you have the Speech Manager Extension installed then have Mac CallerID speak the name of the caller. This way you don't have to run to your Mac to determine who is calling.
Optional PageMe Init String
AT&F0S37=5S4
Also a hardware handshake modem cable is recommended.
Deleting all calls
To delete all calls, quit the application and then throw the MacCallerID.DB file into the trash.
Dialing using modem
Once the phone starts ringing pick up the phone and hit the "Hang Up" button. This will hang up the modem and will prepare the modem to receive another call.
Using AppleScript With Mac CallerID
Take a look at the sample scripts provided and feel free to modify them to suit your needs. Note these scripts only work on registered versions of the application.
When a new call comes you can have Mac CallerID launch an application. Why not write an AppleScript and save it as a built application. The application could get the last call received, launch a database application, find the caller's record and bring it to the front or add the record to the database.
Now you can have other applications notify you via your alphanumeric pager. Other applications that are AppleScript enabled can send a message to Mac CallerID which will call your pager with the message.