Often, the ALV screen of your report is shown correctly, but using any of the ALV functions will cause a dump, mostly with the message GETWA_NOT_ASSIGNED. In most cases this is caused by an error in the fieldcatalog or in the sortfields. Fieldnames in both structures must be in upper case and there must be a corresponding component in the output table. An easy way to find out those misconfigured structures is the ALV consistency check.
You can invoke the ALV consistency check by holding down the SHIFT key and double click with the right mouse button (maybe its the middle button, depends on your mouse/mouse configuration) in an empty area of the ALV Grid, see the pink area in the screenshot below:
After the ALV consistency check is started, you can easily check the layout options, the field catalog, the sort fields and so on. And not even errors are shown up, you should fix the warnings, too. Warnings will be sown shown up if you omit the quantity or currency for example.
Checking the ALV Grid should always be done after development like checking your sourcecode with the Code Inspector.
The consistency check can be done without the mouse in addition. Switch to the list view by going to List->Print preview and enter &SOS in the command field.
In an ALV list the mouse action does not work, you have to enter &SOS in the command field like described above.