Getting the right strength of e-liquid may take a little trial and error, but a good starting point is to choose the strength closest to the number of traditional cigarettes that you're currently smoking a day.
For example, if you're smoking 20 or more a day, we recommend starting with the 18mg strength. If you smoke around 10-15, you'd be best to go for 12mg, and at 5 a day, pick the 6mg strength.
If you're not sure which to pick between two strengths, it's usually better to pick the lower one. This is because, if a vape juice is too strong, it may taste very harsh and cause you to cough a lot, whereas an e-liquid that's too weak will feel just that.
However, feel free to switch up the strengths and try a few, as it may take a couple of different attempts to get right. You can also mix different strengths together to get something 'in between'. For example, mixing a 18mg strength with a 0mg strength in a 50/50 ratio will get you a 9mg liquid.