As payment for goods or services.
Purchase bitcoins at a Bitcoin exchange.
Exchange bitcoins with someone near you.
Earn bitcoins through competitive bitcoin mining.
While it may be possible to find individuals who wish to sell bitcoins in exchange for a credit card or PayPal payment, most exchanges do not allow funding via these payment methods. This is due to cases where someone buys bitcoins with PayPal, and then reverses their half of the transaction. This is commonly referred to as a chargeback.