Are your packets marked already?

1. You need to enable QoS on both switches

2. You need to define your trust domain

3. You need to classify trafic - define which is priority, and which is not

4. You need to setup maps (defaults can be used in mot cases)

5. You need to define bandwidth portions (buffer allocation) or configure expedite queue for priority traffic

6. Optionally you can configure input policies too.

7. Apply it on interfaces.

It sounds complicated, but it's not once you know your traffic and your requirements.

Here is a guide:

http://www.cisco.com/en/US/customer/docs/switches/lan/catalyst3560/software/release/12.2_20_se/configuration/guide/swqos.html

There are a lot examples in the document