Hi Kurt,
Here is what I do. First make sure that you know where your lisp program is located. Next, start Autocad and right-click on any toolbar. In the gray dialog box, click "NEW" and name the new toolbar what you want, then click "OK". (You can also add the new button to an existing toolbar) Your new toolbar will show up in the list with an "X" next to it. There will also be a small empty toolbar somewhere on your screen with the name that you just typed in. That is your new toolbar. Now, click the "CUSTOMIZE" button. Next, in the flyout box that says "Attribute", click on the down arrow and scroll to "CUSTOM". Drag a blank button onto your new toolbar. Now, right click on the new blank button. This opens up yet another dialog box where you can name the LISP program and add the command to activate when you click on the button. In the lower white box you will see "^C^C". These are "Control C's" which will cancel any commands that are currently running when you press the button. directly after the second C (without a space) type the LISP routine's command that will make it run. On the right side of this dialog box there is an area that you can draw a custom button face that will remind you of the command that this button activates. Draw the button face and save it, click on "APPLY" and the button now shows the new face. If you APPLOAD your LISP program and close out all dialog boxes except your new toolbar, then you are ready to go.
Extra hint... If you add the correct LISP code in your ACAD.lsp file (different spelling for different versions) then your new LISP program will be automatically loaded each time that you open a new drawing, making your new toolbar ready to run. If you do not add the code, you can still use the button after you "APPLOAD" the LISP program.
Hope this helps,
Paul