People, I don't think the OP is asking about sending their dog to a pro, they are asking how to know who to listen to on this forum.
How do we novices know to pay attention to on the forum???
I guess you just have to hang out here to get a feel for it.
Some of the posters here are known hunt test pros. There may be field trial pros on here, I am not sure. The pros generally have credibility.
Some of the posters here are known to have had some success (varying degrees) in field trials. If the topics are field trials then listen to those known to have achieved something in that venue, or possibly to field trial judges, depending on the topic.
Some of the posters here are known to be veterinarians. I would listen to them on health/disease/injury topics. A lot of the pros (and some others) are pretty knowledgeable too because of the sheer number of dogs they deal with they see a lot more illness/disease/injury than the average dog owner.
Most anyone here can tell you how to get ready for a Junior hunt test or something like that.
Most anyone can help you figure out what "AFC" means or what does *** mean behind a dog's name.
There are some folks here whose methods are somewhat to very unconventional. If you are following a conventional training program then I would hesitate to follow their advice although you might find something you can use there too.
The bottom line is that it depends on the topic and you sort of have to figure out who folks are. I wish there was an easier answer, but that is the best I can tell you.
Good luck to you and your dog.