When entering an issue/task, the initial status should be "proposed" (unless you're going to work on it yourself immediately).
If you've reproduced the issue, add a comment and the issue status should be "accepted".
To prevent multiple people from working on the same issue, assign an issue to yourself if you start working on it. If you give up, un-assign it and write a comment explaining what you've done/discovered so far.
Once you've checked in changes that address the issue, change the status to 'Fixed' and add a comment to that effect. If you've made a partial fix, you probably need to split the issue into multiple parts.
Please do not Close any issues.
NOTE: These are not fixed in stone, nor do you have to update status every hour. Just periodically mark issues as assigned (in-progress) / fixed /etc so as to prevent duplicated effort.