Job costing is the best way for you to increase your profit and cash flow. This means you need to track the profit of individual jobs. For example, any single job may involve differing costs of labour and materials. You need to work these out and allocate the materials and labour to each job. Once you have completed this task you need to make sure you can easily see the breakdown of invoices and expenses on the job. That way you can work out your gross profit margin.