Before I make a major purpose for anything, I always do a thorough check on the business, especially if they are online purchases. Never ever, go on faith or trust alone.
The BBB is a good starting point. Make sure to also check online reviews of the business (but beware, all posted reviews may not be 100% reliable).
I not only do a check before doing any online transactions, but I do the same for
any major purchase or service. I had an addition put on my home. I checked a multitude of contractors before I selected the one who ultimately did the job. I check to see if they are licensed, insured, if they have workers compensation insurance coverage for their employees, and I check with their prior customers, to see if they were satisfied with the contarctor's timeliness and workmanship. It takes time and some patience, and it might cost a little more, but at the end of the day, i have peace of mind. There are a lot of honest businesses out there, but unfortunately, there will always be a few bad apples too. I am happy to report that I have had no bad experiences (to date) with any purchases I have made from any business, online or otherwise.
Maybe some luck was involved, but I would like to believe that my insistence to do thorough checks prior to making purchases play the key role.