Stuck when trying to paste text from clipboard to xterm via trackpad? You are not alone, it took me a while to find out. Here is a quick how-to, tested on Mac OS X Lion (10.7.5).
Step #1: X11 > Preferences > Input
Set the checkboxes as detailed below
Step #2: System Preferences > Trackpad > Point & Click
Disable Look up option
Step #3: Test it
Copy text to clipboard (cmd + c) and paste it into xterm (alt + left click)
References
