What I tell people,
I sell about 50 cord a year as a one man band. I'm often asked this question by customers that contact me and I have nothing available. This is info I freely give to new potential customers when they contact me and ask about buying.
1- Ask to stop by and see the operation and wood supply. I love it when people do this as it's almost a guaranteed sale. It matters not if you actually plan on stopping in or not. A flat out refusal or all kinds of excuses from the seller should throw up a red flag.
2- Ask for references. Someone they have as a regular customer for at least 3 years, and someone they have recently delivered to. I always have references available. If no references are offered, or you get the run around, another red flag.
3- Ask about the wood. What is the species? When was it harvested? When was it processed? What is the moisture content? What length is it cut to? Anyone that sells wood should be able to and be happy to answer these questions. Ask for pics.
4- Make initial contact by phone. Talking to people will give you a much better feel for the person you're dealing with. You can tell who is proud of their business, product, and reputation.
5- Be sure when they talk about a cord, they mean 128 cu ft. when stacked. There is a huge difference between a half cord (64 cu ft) and a half face cord (22 cu ft).
The above list is by no means a guarantee of quality or quantity but should give you a decent filtering system to increase the potential of getting what you ask for when purchasing.
Good luck
Take Care