How to record transaction for advances from customers, sale and showing debtors in BS

Our company comes under works contract services where goods are the major portion. My query relates to entries relating to sales. Actually when a contract is initiated with the customer, we are debiting the customer and crediting the Project Fixed amount(created in Assets side). So everytime when we receive advance,  cash and customer a/c are being debited and credited respectively. Please help me regarding posting of sale entries. Is there any better idea for these type of transactions??