1) Do not mingle your personal and business transactions.
By using different bank accounts and different credit cards, bookkeeping itself will be easier and bookkeeping cost will be lower.
Keeping Personal and Business Finances separate is always recommended.
2) Avoid Cash because it may be difficult to keep track of your expenses. You are more likely to forget expenses that you could use to pay less in taxes.
3) Reconcile bank accounts monthly (or even weekly if you can)
4) Keep an Eye on Your Invoices, especially the big ones
5) Use cloud-based software to get real-time data