First, you will have to create two Custom Payment Methods - Cash & Check. To do this you will have to click on your profile button on the top right and go to Business Setup:
Then find the tab titled 'Optional Settings', in there you should see a section titled 'Custom Payment Methods'
Then type in 'Cash' and click the Add button, then type in 'Check' and click the Add button. Now you should see both Custom Payment Methods in the list below
2. On the day of the event you will need to got to your Upcoming tab and take registrations from the Roster page for that class. To do this, each time you want to take a new order, click on the '+ New Order' button in the top right hand corner of the Roster page shown below.
On the New Order page, you will first need to choose the customer - either search for them if they are a customer you already have in your contacts, or add them with the 'Add New Client' link.
Once the customer is selected ,you will see a series of fields to complete the order. One of those fields will be 'Select Payment Method'. In the options you should see 'Cash' and 'Check'.
Select whichever option is relevant - either Cash or Check and then you can place the order.
If you'd like to adjust the Order Total you can put a new number in the 'New Order Total' field (ex. if the class is 50 but you are giving it to this customer for 40). To record how much the customer is paying you in cash or check fill out the 'Amount Paid' field. If the Amount Paid is less than the Order Total or the New Order Total this will be reflected in the Order showing the customer still has a balance due. Lastly, you can always add an 'Order Note' if there is any information you'd like to keep with the Order.
You can always see later on which orders were paid for with Cash or Check. Go to Financials > Orders. Then look up the Order number, the customers name or email. Once you've found the order, click on it and scroll down. Then you should see the Payment Method used for the purchase. For example on the one below it says 'Check'.