If you take a look at a Google search for 'eliquid', you will be amazed at how many eliquid suppliers there are out there. Literally thousands, and that is just in the U.S. alone.
This is why you should look for an eliquid supplier that stands out. Not only are they likely to be one of the best ones, but you will find you will get the best treatment from them as well.
What are shipping fees like? -- When I look for an eliquid supplier, I always start off with a look at their shipping fees, as they can tell you a lot about the seller's morals.
Sellers that charge ridiculously expensive prices for their eliquids when it comes to shipping are usually those that are going to scam you. Look for an eliquid supplier with either reasonable fees, or that is willing to ship your order free as long as you spend over a certain amount.
Information about their products -- Do they give you in depth information about their products? If so, this is usually an eliquid supplier that is not trying to hide anything, and likely sells a high quality eliquid.
Are their eliquids made from organic ingredients? -- Some of the best eliquid sellers make all their products from as many organic ingredients as possible.
Always choose such a seller first, as you will be getting a superior e-juice.
Do they manufacture their own eliquids? -- Although these eliquid suppliers are rare, try to find one that manufactures their own products.
If you can, you will be guaranteed a high quality product that has been tested along its manufacturing process for quality, and has the best quality control functions in operation at all times. Pretty much guaranteeing a high quality eliquid.