Collecting payment from customers requires a means for extracting funds from the payment method the customer chooses.
If you offer check/money-order, then it's up to them to send the check to you. Naturally, you will typically wait for the check to arrive and clear your bank before shipping the goods.
Before you can accept credit cards directly you must have a merchant account.
If you offer to let your customers pay by Credit Card, there are a couple ways to do this:
a) An online banking service such as PayPal