These photos look so pretty and are surprisingly easy to achieve! Follow my easy guide to get some smoke trail photos of your own. 

You will need:

• Black Cloth or Foam Board for the background
• Tripod for your camera
• Off-camera flash (I used a Canon 430EX II)
• A way to trigger your off-camera flash. The pop-up flash on my Canon 60D acts as a master flash and can trigger off-camera flashes. If your camera does not have this capability, you will need radio slaves (I recommend Pocket Wizards) or cables to make your flash go off.
• Incense plus a holder for it
• Lighter

Set-up:

• You want a well-ventilated room that is somewhat dark and not too drafty otherwise any slight change in airflow can disrupt the smoke.
• Put up your black background.
• Set your incense up on the holder. At least 1 foot in front of the background.
• Place the flash off to the side, behind the incense. Try not to let the light fall onto the background. 
• Place your camera sturdily on your tripod, 2-4 feet away from incense depending on your focal length and how you want to compose your shot. I used a 100mm lens so my tripod is set up farther away, but ANY lens should work.
• Set the following settings on your camera:
  
  • Camera Setting - Manual
  • ISO - 100 (or the lowest number your camera can go to). This reduces the graininess of the photo.
  • Shutter Speed - 1/250. You want it fast to capture the movement of the smoke.
  • Aperture - Somewhere between f/8 to f/22. I used f/22 with my 100mm lens which already has a very shallow depth of field. Keep your aperture small (meaning a larger number) to get as much as you can in the depth of field.

Taking the Shot:

• Focus. I focused on the incense stick to start but adjusted depending on where the smoke was blowing. I suggest manual focus as needed.
• Light the incense.
• I like to lightly fan the incense using my hand to create some interesting shapes. You can also place an object like a spoon above the incense stick.
• Try out some test shots! Adjust as needed. You are aiming to get the background underexposed to a pure black and the brightest part of the smoke should be white.
• When you're happy with it, shoot away! 

Bonus idea: Create different color smoke by adding a gel to your flash or select "Multiply" on a colored or gradient layer in Adobe Photoshop! The examples at the top of the page where used with a rainbow gradient layer. Example of a colored layer: