An increasingly common feature among AV receivers is automatic calibration, which makes it incredibly easy to optimise the sound characteristics for your listening environment. Receivers with this feature come with a microphone that plugs into the unit's front panel.
Place the mic in your usual listening position, hit start and the receiver automatically runs through a set of test tones, which are picked up by the mic and fed back to the receiver. It then analyses the information and sets the appropriate delay, distance and volume settings for each channel. It saves you the time, hassle and guesswork involved when setting everything manually, which is often a godsend for those not versed in the science of audio calibration.
Another socket you may find adorning the back panel of certain high-end receivers is an Ethernet port. In some cases, this allows you to connect the receiver to your internet router and conveniently stream media files from PCs elsewhere on your home network, which means you don't have to load those files onto a disc or USB stick and physically bring them into the living room. Some units also use this connection to access internet radio stations, the beauty being that you can listen to them in better quality than your PC or laptop can deliver.
Among the other tricks to look out for are audio lip sync settings, which can set a delay to correct any issues you may experience when watching movies. A good onscreen display is always welcome too, making it easier to tweak the settings than the front panel - Onkyo and Marantz's latest models are great examples - and look out for THX certification, which means that the receiver meets certain specifications laid out by George Lucas's company, a guy who knows a thing or two about movies. These are determined according to what the THX experts think constitutes the best-possible sound for movies in rooms of different sizes.