Sometimes it can be hard to increase your sales as people only have so much money and no matter what incentives you throw at them, they are not biting. But, if you do it right, you can get bookings from your desire to increase sales and it works, because you now have another party to get sales at, right?
When you do a party, you should always have guests writing down what they want to buy. Whether you give them a checklist, a mini catalogue or a scrap paper, they should have a writing utensil and somewhere to mark items on. Tell them to mark with a star the items they really want and a check on those they are not sure of and to bring it with them to order.
When assisting them with their order, you want them to bring their list with them and give it a quick glance. If they are already ordering everything on it, you can ask them if they are interested in getting some of it cheaper/free if they have a party. Accept their answer either way and finish the process. If you see that they have a lot of items marked, but their order sheet is short, ask them if they are still interested in those other items that they weren’t able to order and discuss with them having a party. Even if they turn you down, encourage them to keep their sheet (which should have your contact information) as they may decide later that they truly want that one item.
If you can get a booking out of this method, then you have in essence increased your sales on this party as you got another party you may not have gotten otherwise.