In your Seller Admin > Payment Preferences screen, we have a checkbox to ONLY AUTHORIZE the payments and charge them manually from the payment processor's interface (not available for TrialPay, ClickBank, 2CO). Enabling that setting will tell your payment processor(s) to verify only that payment amounts can be charged without actually charging them, putting these payments on hold for you to approve manually.
Note that enabling this setting also disables the setting Wait for pending payments (excluding payments manually being reviewed by payment processor) to clear before processing them, so our system would process these orders as soon as the payment is authorized, rather than waiting until after you manually approve the payments.
We do not have a way at our end to set payments on hold and only process orders after you have approved the payments manually. However, PayPal and Google Checkout can set at least certain types of payments on hold at their end, such that they would only send confirmation of completed payment back to our system once you approve the payment, and then our system would process the order. Contact their help pages or support staff for further details on these settings in their system.