We've got lots of existing meta posts about how many bad questions there are and how much of a problem they are (or aren't) - that's not what this question is about.

I wanted to collect in one post some techniques for finding bad questions and dealing with them and it should come as no surprise that by "dealing with them" I mean to downvote the bad ones.

The automatic delete rules are our friend here: questions with no answers and negative scores (or 0, or even +1 in some situations) will be automatically deleted if they meet certain criteria. I'll be posting some of the searches I do to find bad questions and anyone else who has ideas can do the same.

Here are the automatic deletion rules:

9 Days

If a question was closed more than 9 days ago, and ...

• was not closed as a duplicate
• has a score of 0 or less
• is not locked
• has no answers with a score > 0
• has no accepted answer
• has no pending reopen votes
• has not been edited in the past 9 days

... it will be automatically deleted. This check is run every day. (at 0300 UTC)

30 Days

If a question (open or closed) is more than 30 days old, and ...

• has −1 or lower score
• has no answers*
• is not locked

...or if it was closed and migrated to a different site...

... it will be automatically deleted. This check is run every week. (0300 UTC on Saturday, to be precise.)

*NOTE: In most SE contexts, "no answers" means "no answers with a score > 0" i.e. no upvoted answers. But there are comments on Reference #2 that imply this auto-delete scenario only applies to question with no answers whatsoever.

1 Year

If a question (open or closed) is more than 365 days old, and ...

• has a score of 0 or a score of 1 with a deleted owner
• has no answers
• is not locked
• has a viewcount <= the age of the question in days times 1.5
• has 1 or 0 comments

... it will be automatically deleted. This check is also run once a week.

References:

1. The official FAQ post on meta.SE about how deleting works. The first answers includes the rules for automatic deletion, and links to more detailed explanations given in the next reference.

2. The post on meta.SE that most clearly states when "bad" posts are automatically deleted. This includes a new rule for automatic deletion that was added in June 2013.

3. Since the automatic delete rules mention locked questions, here's the official FAQ post on those.

4. Duplicates

My post on meta.SE asking if the auto-delete rules apply to questions closed as duplicates is the closest thing there is to an official answer. And the answer is: Duplicates do vanish, so the auto-delete rules apparently apply.

This isn't official since there's nothing posted by SE employees, but it explains what the observed behaviour is: the same autodelete rules apply to questions closed as duplicates. There's a link to Shog9's answer to another question that implies that crappy duplicates deserve to be deleted.