Getting noticed
Whether you have an online store or a bricks-and-mortar one, if you are accepting bitcoin, you need to publicize that fact with a sign. You can, of course, make your own, or grab the 'bitcoin accepted here' sign from the bitcoin wiki.
DIY payments
If you like to have full control of your website and you have some coding skills, you could accept bitcoins simply by posting your wallet address or QR codes for customers to scan with their smartphone cameras. However, this not only looks very basic, but also accomplishes only half the job, as you should ideally have a checkout procedure that will complete the transaction and accept delivery details.
If programming your own payments interface, bear in mind it should continually create new wallet addresses to defend against “taint analysis”, which could invade your privacy, as well as that of your customers. An open-source software library that can help with this is Pywallet. You can also use off-chain transactions to help prevent taint analysis snooping, with the added benefit of faster transactions.