importantfirst learn about bitcoin, educate yourself about security, how a wallet works, the risks of losing your wallet (like getting hacked) if you are not careful and how to prevent them, and risks of price fluctuations, learn about fees,...
then start accepting bitcoin.
option 1:
is what everyone else already said. use a third party escrow.
option 2:
learn what Multisignature means and use that as your "customer safety net".
in short you and your customer each create a key and share the public key. in order to create a transaction both of you need to sign the transaction. customer makes the payment to the multisig address you created, you see the funds there so you ship the goods. with it you also spend the funds and half-sign the transaction and send it to the customer to sign it again. he receives the goods signs the transaction and finalizes the transaction. this is 2 of 2.
you can also use a 2 of 3 one with a third party and don't have to fully trust them.
[1]
https://en.bitcoin.it/wiki/Multisignature