For instance if you don't expect less than a couple of payments per month then going with a payment processor like Bitpay may not be the best idea. setting up a simple light (SPV) wallet such as Electrum and accepting payments that way is a much easier option. you can print out the QR code of a single address and stick it in front of the cashier with a bitcoin is accepted here sign so that if anyone wanted they can pay that way.
if it is more number of payments then you may want a more elaborate setup and possibly think about setting up a full node instead of an SPV wallet and generate a new address for each payment.
and if it is a lot of payments and you want the fiat equivalent so that you never have to worry about the fluctuations but also if you are ok with the fees they take from you then use Bitpay.