There's a few ways to do this:
1) You can add asterisks to the title of items like this: *** Modern Luca Glider Chair ***
2) You can add a note to the note box on individual item to give them a priority rank. (i.e. high, medium or low priority)
3) You can create a custom category for high priority items.
To do this, click "Organize Items" just above the first item on your registry.
Then click "Organize Categories".
You can create the custom category there.