#1 is safety by default.
#2 thing I do is look at the accounts of people leaving the best reviews. I normally see sales threads where I'll see a streak of accounts, all registered within the same 3-6 month time frame, all with less than 50 posts, then I will click on everyone one of those people to see where they posted previously. I've eliminated a lot of sellers this way. Cause I'll regularly find accounts where a person has 8 posts, and 3 or 4 of those 8 posts are in 1 sales thread.
#3 in alignment to the previous, I look for people posting the line, "service looks great, just marking for future use so I don't forget". That shit is shady as hell. There are a few top sellers on here who have A LOT of posts like that. People with 2-3 year old accounts bumping a thread to "mark" it. And I wonder "you've been on this forum for years and still don't know how to BOOKMARK a thread? you're gonna BUMP it so it disappears in a few hours ... how the hell is that gonna help you 'not forget'"?! It's obvious (to me) that seller is using dummy accounts to bump their own service. If I see any of this or #2 patterns most of the time I'll scratch a person off the list. Or I'll order then leave an honest review if I think a service is FOS.
#4 I look for bluename clients or old yellows posting SCREENSHOTS of rankings. For example, CeasarSEO at Warrior Forum (service shutdown now but you can still see what I mean) he had MANY old clients posting screenshots and details about how well they were ranking. Which is why I used him for many years. And he had tons of repeat sales as well which is another huge thing I look for.
#5 the sales page. The more cartoony a salespage looks the less likely I am to order a thing from it. Sellers say they do this to be "fun" but it's stupid. This isn't a gaming or movie forum it's a marketing forum. Learn how to copyright. And I'll tell you how you can be "fun" or look "fun". Try to be unique and rather than waste all your time making a lame ass movie / game based salespage.... try putting that time into the results you deliver for your customers. That's how you make a service "fun".
#6 how the seller responds to complaints. I read these very carefully. The seller should never try to shift accountability. If I see a smarter marketer I know, who I know knows how to make good sites, using a service and not getting any results month after month, and the seller keeps trying to blame everything but his own shitty work, again, this is a huge red flag. I like guys who are accountable and willing to accept responsibility.
#7 transparency. It's perfectly fine if you don't offer samples or reports. Especially if you're selling PBN links. But if you intentionally leave very critical shit off your sales page, mislead or misrepresent anything in anyway, I don't trust you and I'm not using you.
#8 this is almost unheard of. And again I hate to bring up CeasarSEO but till this day he's the only provider I know of who ever did this. He intentionally rejected roughly 15% of all new orders and clients. If they were new members, people he couldn't identify or trust, he had no problem refunding their orders and rejecting their campaigns. That shit was genius. If I see a seller doing THAT, I'm 100xs more likely to wanna order. Cause like I said, almost no sellers on BHW even think of screening clients on here. I have no idea why cause it doesn't just make your network / links safer, but it's an excellent marketing tool and shows me that you're a smart fucker who knows what he's doing. It genuinely scares me when I see a newly registered member with 4 posts ordering a very popular PBN service and the seller won't think twice about taking their order. You have NO IDEA who that person is. If they work for Google, if they're a competitor trying to take down your network and I wish more sellers would start doing this. SCREEN YOUR FRICKN CLIENTS PEOPLE.
There are lots of other things I look for but those are things I pay most attention to.
-BB