How to determine which tasks are higher priority than others?

JIRA offers voting mechanism that helps determine the number of people asking for a task as well as who these people are. JBoss Project Leads consult these votes in order to schedule tasks. All other developers in a project coordinate their time and tasks with the project lead. A select number of stakeholders have overriding power for task priorities. The JBoss CTO has the highest authority on development task priorities. When there is ambiguity on task priorities, contact your project lead or development manager.

Here is a link to the voting form for a sample issue:

http://jira.jboss.com/jira/secure/ViewVoters!default.jspa?id=10021