You can put a question up for a vote:

• When there are two or more answers to your question.
• After the question has been up for at least 4 hours.
• Within the 4-day open period and before the question expires.

To put a question up for vote:

1. Go to the question.
2. Click Edit in the action bar below the question.
3. Select Ask for a Vote in the edit menu.

If you take no action and the question expires, it automatically goes to a vote.