Bank Account Reconciliation- Many small businesses make the common mistake of waiting for a bank statement to reconcile their accounts, but bank statements are only mailed monthly. That means you have roughly 30 days between reconciliations, and a lot can happen in 30 days. You should at least reconcile all of your cash accounts weekly. If you have the time, daily is an even better option
Vendor Payments- You need a system for vendor payments. This is vital for keeping track of your debts, and it's also important for establishing a good reputation and credit history with your vendors. Your payment terms will vary from one vendor to the next, so you can't get by with paying bills only once a month.
Customer Receipts- The only thing worse than an unhappy vendor is an unhappy customer. No one likes to pay a bill, then receive a "past due" notice a week later. To avoid this situation, make sure your customer receipts are recorded in a timely fashion. Daily would be ideal, but weekly should be sufficient, too.
Other Transaction Entries- Vendor payments and customer receipts will make up the bulk of your transactions, but you probably have others, too. Auto-debits, interest payments, and bank fees are some common transactions that you'll need to record weekly. Most bookkeepers choose to record these before a bank reconciliation to make the process as smooth as possible.