Voice bearer traffic typically uses the EF (Expedited Forwarding) DSCP value (DSCP 46) rather than AF. IP phones will typically set this value themselves, as well as a CoS value of 5 at layer 2. If you don't want to get too much into the details of QoS and queueing, you can use Cisco AutoQos to configure some basic QoS for you. I wouldn't recommend it for a very large scale deployment though.

http://www.cisco.com/en/US/docs/ios/qos/configuration/guide/autoqos_voip.html

You can also look at AutoQoS Enterprise, which uses NBAR to identify traffic classes.

http://www.cisco.com/en/US/docs/ios/qos/configuration/guide/autoqos_enterprise_ps6441_TSD_Products_Configuration_Guide_Chapter.html

HTH

If you are using per hop behavior you must mark as close to the edge rtp with value EF and in the rest of the devices police EF packets in the low latency queue if your are using CBWFQ with LLQ.

This is a short advice. Kind regards

I would recommend a Cisco ONT book or maybe CBTNuggets or Train Signal Cisco ONT CBT.

Setting up QOS on a network for VoIP requires much research so you don't bottleneck other types of traffic on your network.