Bugzilla has a "voting" feature. Each product allows users to have a certain number of votes. (Some products may not allow any, which means you can't vote on things in those products at all.) With your vote, you indicate which bugs you think are the most important and would like to see fixed. Note that voting is nowhere near as effective as providing a fix yourself.
Depending on how the administrator has configured the relevant product, you may be able to vote for the same bug more than once. Remember that you have a limited number of votes. When weighted voting is allowed and a limited number of votes are available to you, you will have to decide whether you want to distribute your votes among a large number of bugs indicating your minimal interest or focus on a few bugs indicating your strong support for them.
To look at votes:
To vote for a bug:
You will automatically get email notifying you of any changes that occur on bugs you vote for.
You may review your votes at any time by clicking on the "My Votes" link in the page footer.