Ah, nicotine. The reason that vaping is even relevant at the end of the day. Choosing the right strength can be as hard as choosing a device, if not more so, and choosing to have too much or too little can drastically change your experience of vaping if you're just starting.
Now having nicotine in your juice is absolutely optional, and if you don't/didn't smoke before absolutely do not get liquid with nicotine in it. Nicotine is highly addictive, and you should not consume any if you have a relevant medical condition or are pregnant. But if you smoke and are looking to try vaping to help you get away from cigarettes, nicotine is going to be the expediting factor when it comes to how easily you can get away from them.
When it comes to amount, it really depends on you. You won't know what is too much or too little until you try, but here are some tips to help you start in the right place:
1. Are you using or planning on using a 'Sub-Ohm' Tank? If so don't go with anything higher that 6mg right off the bat. These tanks are meant to provide a lot of vapor and flavor, but also deliver nicotine with hyper-efficiency, I can promise you that a 6mg will hit as hard as a cigarette and then some. Even if you are a multiple pack a day smoker, don't try and show off by getting a 12mg or more, you will just hate the experience and make yourself feel gross.
2. Do you smoke every day, or just casually? If you smoke every day I would at least get a 3. I have had a lot of people say they are a 'habit smoker' when they smoke half a pack a day. While I do respect that there is a habit element in how much you smoke, at the end of the day there is a chemical addiction in there that keeps you on the cigarettes, and after a week or less of no nicotine that addiction will rear it's ugly head. (If it didn't you probably wouldn't need vaping to quit). So if you do smoke every day, save yourself some time and get a 3mg liquid.
If you smoke casually (like a parties or when around other smokers) you can probably get away with no nicotine, you'll know the addiction when you have it and if you can go weeks or months without having an urge to smoke, you shouldn't get nicotine in your liquid.
3. Start low, and work your way to what you need. If you are at or around a pack a day, start with a 3mg, and see how it treats you. If you find that it is effectively satisfying the craving and you are less inclined to smoke cigarettes, you're probably good where you are. But if you still smoke regularly with the strength you have, stop in and get your juice bumped up a step. It's easier (and cheaper) to start with a lower strength and work your way up to the strength that is right for you, than to aim really high and hate the experience.
4. Vape the strength you need. A lot of people vape to quit nicotine all together, and vaping is an excellent way to accomplish that. But again, if you smoke every day you have a chemical addiction that wants to be satisfied. If you feel right with a 6mg, vape a 6mg until you feel comfortable going down a step. The benefit (and I say this not as a medical professional, but a long time user who benefits from vaping over smoking) to vaping is that there is no rush to cut back, take your time, and go down as fast as you feel comfortable. If you do, you can easily find yourself at 0mg or quitting vaping and smoking all together without the stress and withdrawals of going too fast or cold turkey.
Now the other thing you'll want to think about is the flavor you want, one of the things that's appealing for vaping is that unlike the wet-dirt like taste of a cigarette, vaping can be quite a pleasant experience if you have the right flavor. So what do you start with?
Well the go to seems to be tobacco flavors, they are a familiar flavor to those just quitting cigarettes, and there are quite a few people that enjoy it even after the beginning transition. What I've found with new vapers is that tobacco flavors are good until your sense of taste starts to come back. Because if you stop smoking cigarettes for a week or two, you'll start to realize how... less than spectacular tobacco tastes. So something you may want to think about is grabbing a bottle of tobacco flavored liquid, and something different. Even if you just go with something generic like a Grape Soda or a Churro Chunk Praline Ice Cream (I had to throw that in there, it's my favorite) Just to try out if or when the tobacco charm starts to wear off. It will help you transition fully away from cigarettes and into the world of vaping without a lot of growing pains.
In conclusion, the best way to know what you need is to try it first hand, so stop by your local Vaping The Way and let us help you quit smoking cigarettes.