It's simple, really. Check if the closed question should really remain closed right now. The purpose for the Reopen Queue is to give a chance to the questions that probably don't deserve to be closed.
So, that would mean questions closed as Ubuntu+1 (mostly closed as off-topic or duplicate of There's an issue with an Alpha/Beta Release of Ubuntu, what should I do?) at the point of asking should probably be given a second look.
Maybe just those that aren't asked again and is still relevant after the version release and optionally, also has a good answer. An example of the above - Where is "Show position of the mouse when the Control key is pressed"
Other than that, here's a general advice for using the reopen queue.
For questions closed as duplicates, check if the question is really a duplicate.
- Do both the posts ask the same question? If no, vote to reopen.
- Does the answer on the duplicate of good to great quality that it deserves a home in the master question? If yes, flag for merging the question.
For questions closed as off-topic, check if the question is really off-topic.
- If the question is indeed off-topic and has no good information in answers that is worth preserving, consider if it should be deleted from the site. If yes, flag for deletion.
For questions closed as "Not a real question" and "Not constructive", check if it deserves a place in our site. If no, flag for deletion.
For questions closed as "Too localized", check if the question is well phrased, contains enough information to suitably answer the question and is still relevant for the modern time. If yes, vote to reopen.
A final piece of advice.
When in doubt, don't. If you are not sure what to do with a review item in the reopen queue, skip it. Remember, it's most preferred instead of a wrong 'Reopen' or a 'Leave Closed' action.