I have been lifting for over 15 years and have never once hired a trainer. Waste of money in my opinion.
I have a buddy that counsels people in his gym for free. They will hire a trainer, then see him lifting (he is the biggest guy in the gym...it's a fitness center and he is 260 at 10% body fat) and ask him what to do. He shares whatever information which almost always contradicts the trainers or at least exposes their lack of knowledge. Two people at that gym have fired their trainer because of him. I feel like he does a great service to aspiring lifters there, haha.
And surprisingly, they have not revoked his membership yet.