My best advice is to 'vet' people. With me, I trust just a few people in the nutrition and fitness industry, why? because time and time again they talk sense, they know their stuff, and they have proof that what they do and say works. There are a huge amount of 'wannabe's' out there that, to be frank, talk utter rubbish, those are the people you should NOT listen to. A group of people that I have never followed or listened to and never will, are 'Herbalife distributors'. I have had 7 follow me, and when they realised I didn't follow back, they unfollowed me. They are just salesmen, and ridiculously bad ones at that. None of them looked in shape, or showed any kind of affiliation with fitness and nutrition, they just flogged Herbalife's awful products. If people seem more concerned with money, selling their products/programs/services, than actually helping people, then run away!!
Not every trainer is 'jacked' with muscle. Some of the best trainers in the world aren't huge, they are simply healthy, so the amount of muscle mass doesn't actually matter that much. Two very successful trainers couldn't be more different - Nick Mitchell and Bob Harper, but they get amazing results in their areas of fitness. But if a trainer is overweight or just unfit (struggling to keep up with their clients) then they are a big 'no no', those are the people to stay away from. I won't name who this person is, but I remember a trainer I came across on Twitter and he wasn't in shape at all, had pictures of him getting drunk a lot, even eating take aways all the time etc etc... He preached his beliefs, he disagreed with my tweets a lot, and it got to the point that I simply couldn't be bothered reading his garbage anymore so I blocked him. You get a lot of those kind of people unfortunately. If someone is a trainer/nutritionist or anything similar, they should be healthy, fit, in shape, and do as they say. Why would you listen to someone telling you how to lose weight, when they are overweight themselves??
The best thing to do, is find a few people that regularly post on social media / their websites / their blogs or on Youtube, and if they talk sense regularly, talk about worthwhile things, they aren't just trying to flog their programs or systems, follow them! listen to them! because they are most likely 'the real deal'. Try and avoid people that seem (sorry for my bluntness) way too far up their own ass, because a personal trainer or a nutritionist is there to help others, understand others, give other people happiness within themselves, NOT to show off their body 50x a day or go on and on about how much they bench!
As always, be smart, don't get conned, and find a few people to trust. My main 'source' for information in the fitness and nutrition industry is Nick Mitchell (you should give him a follow....he knows a few things!)