First: Heat, Light and Air

Firstly, you would usually keep your e-liquid away from heat and sunlight. These may lead to your e-liquid getting darker, and could speed up nicotine degradation. (This is not the case for accelerated steeping.)

The other thing to bear in mind is that if your e-liquid is exposed to air, impurities could get into your e-liquid. The propylene glycol in your e-liquid should kill any germs off, but it is still something to bear in mind.

Now, there are dozens of ways to steep e-liquid. Spinfuel magazine advises keeping it simple, at least to start with.

But for the sake of completeness we have include a selection of different steep methods for you to play with! You’ll find many more on forums and Reddit.
The Slow Method

The first method simply involves periodically shaking your e-liquid, and the rest of the time leaving it in a cool, dark place.

Most people will either remove the cap and leave the cap off, or periodically take off and replace the cap. However, E-Liquid Zine references an interesting experiment where steeping was carried out without removing the cap. The results were the same!
How long should you steep e-juice for?

Unfortunately, there’s no one answer. It depends on the e-liquid you use, and, of course, your personal taste. In fact, we find some e-liquids don’t need any steeping at all…

To get a clearer idea of steeping for different flavours, we asked our own mixologist, Will Brunton, to comment…

Custards and Complex Dessert Flavours

2-4 weeks is usually ideal. However, some flavours can be left even longer. Some people argue that these flavours continue to improve after several months of steeping.

Fruits and Menthol

Either shake and vape, or leave up to 2 weeks. Most fresh fruit and menthol flavours won’t require much, if any, steeping before use. Many of these flavourings react poorly to breathing in particular, and can lose flavour when this is done for too long.

However, more “creamy” fruit flavours such as Mango or similar can benefit from a week or two of steeping. The same goes for very complex fruit mixes, as this allows time for each component to “bond” and create the desired overall flavour profile.

Tobacco

Shake and Vape, or leave for 2-4 weeks. The majority of Tobacco flavours will benefit from a couple of weeks steeping. They tend to be quite complex flavours, and require this bonding time to really pick out the subtle flavour notes.

On the other hand, most tobacco eliquid vapers tend to be happy with the flavour when freshly mixed. I would argue that this is because some flavours used in tobacco are unfamiliar to the usual palette, so it will be difficult for most people to detect change even in a steeped bottle.

This does differ with Tobacco e-liquid containing flavours such as Caramel and Vanilla, as most people will notice the benefit and flavour improvement steeping such eliquids for 2 weeks or so.
Accelerated Steeping Methods

Steeping Icons 3

First, a quick thanks to all the many vapers who have experimented and documented accelerated methods of steeping. I’ve included a selection here, but you’ll find even more steeping methods listed in the resources as the end of this post.
Stir

At ECigaretteDirect, we’ve experimented with a magnetic stirrer to speed up the steeping process. The advantages are that air is mixed into the e-liquid at speed, but the results didn’t seem to be as good as leaving the e-liquid in a cool dark place for several weeks.
Ultrasonic Cleaner

Various vapers have tried using an ultrasonic cleaner to steep e-liquid, with mixed results.

Bobalex from E-Cigarette Forum uses a 2.5 liter ultrasonic cleaner to run e-liquid bottles through mixed warm and cold cycles. You can see his full description here.
Heating Methods

Most vapers will tell you glass is best for heating methods. Glass retains heat better and melts at a much higher temperature.

However, the melting point of most plastic is comfortable above that of boiling water. In fact, while writing this post, I experimented with pouring boiling water on to a bottle of Halo E-Liquid. The bottle was fine.

That’s not surprising – the melting point of the plastic used (PET) is 260 degrees celsius.

What about leaching chemicals, you may ask? That’s a controversial subject, but the PET resin association claim that their plastic is very inert.

Even with glass, though, you avoid high temperatures. While warming can speed up the steeping process, too much heat can degrade the nicotine and flavourings.
Warm Bath

    Heat some water. The water should be warm, not hot.
    Place the capped e-liquid in a sealed bag (some vapers recommend two bags.)
    Drop the bottle in the water, leave for 10-15 minutes.
    Remove the bottle and cap and shake. Test the e-liquid. Repeat until you get the desired taste.

Ideally, you would have water at a controlled temperature, but this is probably going a bit too far for the average vaper.

The Rice Method

Place a cup of uncooked rice in a microwave. Heat, then place the e-liquid in the rice. Leave till it reaches the desired temperature, remove, shake. Repeat process until the e-liquid achieves the desired taste.
Shotgun steeping

Tie a bottle of e-liquid in a sock. Put it in the dryer and put the dryer on for fifteen minutes. Vapers who have tried this have seen a noticeable difference in the colour after just 15 minutes.

They have also experienced damaged bottles and escaping caps, so be careful (and don’t use this method with glass bottles!)

The Hot Car Method

Put your e-liquid into the glove box of a hot car. Leave for a few hours, remove and enjoy.

Additional Resources
Steeping E-Juice (Vaping 360)
Steeping Video (Rip Trippers)
How to Properly Steep Your E-Liquid (Zodist)
Speed Steeping E-Juice (OnVaping)
Steeping E-Liquid (Spinfuel Magazine)

How do you steep your e-liquid? Do you think it makes a difference? Let me know in the comments!