Have you ever noticed how many people have advice to give when something in your life is changing? Marriage, divorce, pregnancy, decision to lose weight, eat healthy, etc.. Most people are well meaning, but every once in a while you get stuck in the bucket full of crabs. Just when you're trying to do better, or be better, they want to yank you back down.
I was trying help my son understand this very concept recently. He injured himself and everyone at school had something to say about it, even the principal! I explained to him that sometimes you just have to smile, nod, thank the person for their input and move on. Sometimes as adults we forget this and allow others to derail us or cause us to question ourselves.
I talk to people every day who struggle with reconciling all the information and opinions they receive. Health and Fitness are two of the topics about which people seem to have the most opinions. What often makes me chuckle, is there are no facts to support this "wisdom". Why then, do any of us listen to our friends' advice? Is it because they look the way we want to look? Have the lifestyle we envy? While I absolutely agree that if you want something, you should seek out someone who has achieved it and find out how they did it. I also believe you should exercise caution in doing so. The workout or eating plan that your friend is on, may be working perfectly for them, but it may be the polar opposite of what your body needs. Seeking out professional advice is never cheap, but it usually beats the alternative. Taking advice from a friend could land you several months down the road with the opposite effect you were seeking. Then you're not only back to square one, you're behind square one. If you take the advice of the next friend, the cycle may repeat or worsen.
There is a lot of great free information out there. I suggest using what I call "The Filter Effect". Whenever you hear something that sounds like sound advice, filter it through your own common sense, then filter it through your own experience. Finally, consider the source. If it makes its way through all of those filters, it might be worth a try. You can also use this method to analyze all the information you get from the media. First, filter it through a list of things that you've already seen, tried, read or heard, then filter it through what you know about your own body. You know more than you think you do. If, after considering all of that, it still sounds like a great option, give it a try.
I would caution you against following the latest trends or the advice that the guy at the gym gave you. When in doubt ask someone who knows for sure. I'm always happy to answer questions and I know many of my fellow fitness professionals are as well. Of course we all have our own opinions, but usually we have a little bit more knowledge to back them up.
Best of luck on your new journey!