If you register on a reputable exchange, buy some BTC with fiat and then withdraw it to your crypto wallet, you'll definitely know the coins exist when they appear in your wallet. Use reputable exchanges, wallets and cryptocurrencies, and you'll avoid scam. And if you mean fake trading volumes that exchanges report, this is way harder to check and is unfortunately a serious problem. I don't trust the reported volumes after the scandals that occurred, but it's fine to choose exchanges based on other things like the number of active users and, most importantly, reputation.