As long as you have the hardware set up correctly to take advantage of dual monitors, it's pretty easy. We have an old split view tool that's been in the software for years, it's ok but not great. Our newer tool is better...If you want to take the forms tab to a different monitor, while in data entry click the F button on the far right of the top button bar. This will take the Forms (review) screen to your second monitor automatically.  So, when entering data on monitor 1 you can see the changes to the forms and schedules on monitor 2.  We added a D button as well, so if you have 3 monitors you can see data entry, diags, and forms on three separate monitors.  

Clicking the D and F buttons will activate the feature just for that session, if you shut Lacerte down and open it gain it will revert back to not putting the diags and forms on your other monitors. If you want always have this feature "on", go to Options/Settings Tab...at the bottom of the first section find the option that says "auto pop-out Forms and Diagnostics" and set it to yes.