When changing lanes, you should:

• Make sure that there is no traffic ahead or behind of you in the lane you would like to enter.
• Check your mirrors for any vehicles that are preparing to pass you.
• Use your turn signal to alert other drivers of your intention to change lanes.
• All of the above.
  Explanation:

  "Follow these rules when you are changing lanes: 1. Make sure that there is no traffic ahead or behind you in the lane you would like to enter. 2. Check your mirrors for any vehicles preparing to pass you. 3. Use your turn signal to alert other drivers of your intention to change lanes. "