Network traffic priority best practices at switch level

What is usually the best way to prioritize specific traffic from a specific VLAN?

I am working with Differentiated Services to match traffic from a specific VLAN and assign a switch queue of 6 to give this traffic a higher priority than normal traffic. But I am not sure with this configuration. I've red much about switch traffic priority but I didn't understand it all i think.

The policy is definitely working. In the web interface I see that are packets offered for this DiffServ, I think I am missing something...

Config:
policy-map {policy name} in
class {class name}
assign-queue 6
exit
interface port-channel 1
service-policy in {policy name}