Some people are lucky to have a real non-ripoff ecig shop near them, one that sells liquids and parts. Most people buy on the web. Buy extra in the beginning (spares parts, extra liquid) so you don't run out and then over not too long you will accrue a collection of juices including some you don't like so much but they would work if you got caught short. The main time people run out of juice is when they first start - they don't order enough with their kit and or order subsequent juices from a slow place that just had a big sale, and get caught short.
Some tips
Nothing the diameter of a cigarette will be strong enough for a full-strength smoker to be anything but a way to waste money before buying something decent
Buy an ecig with manual batteries - autos are easier to kill with juice drips, many autos can turn on accidentally from wind or vibration, and manuals give more control of your hit. The most popular methods of vaping - dripping on an atomizer and using cartomizers - are both ways to kill auto batteries with leaked juice.
Ignore the entire seedy upper crust of ecig sellers with their lies and jacked up prices and mystery brands.
Prefilled is only a small convenience - you need eliquid for all kinds of vaping
Ecigs to look at (as manuals!)
Joye 510 - short battery life (2-3 hours for a light to moderate vaper. 1/2 that for a heavy vaper). Manual batteries totally sealed on the threaded end. Few prefilled cartomizers, lots of blank cartomizer type, the most supported threading
Joye 510 w/ mega/xl batteries - 60% more charge life but may be a bit long for a guy. 128mm long with a cartomizer *the way I use 510s)
KR808D-1 (and Vapor4Life.com in nice colors, most prefilled cartos are there) - this is a 2-piece. Lots of prefilled cartomizers, plenty of blank cartos. Manuals still have a hole in the end but at least there is no drag sensor in there to be gummed up with juice. Standard battery is 120mm long w/ a carto on and same charge life as Joye Mega xl. To drip you need a DSE901 atty
Then there are the fat battery models with super-long charge life - like Joye Ego and Riva 510 in 510 threading and LeCig's Pigcig or CigEasy's Elegant Easy in KR8 threading. Fat battery models can also sue low resistance parts that run hotter (and use battery charge faster) for hotter hits and more TH
Adapters are also available for 510 and KR8 for use parts of each other's as well as other models.
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That's why Big 
