If you're after a secret for training, I get the idea you're losing motivation. Because when you're motivated, you just get it done and watch the gains come in. Try hiring a personal trainer at a decent gym, I used to workout at Pure gym chains, with the WORST commercial gym music and a vibe of people that couldn't be arsed. I joined my local gym in stoke called Apex and found a PT that actually fired me up for every session.
Once you're fired up, the hardest part is to stay on top of your diet, which for me was eating MORE food than before, I find it difficult to put weight on.
Check with your gym or search for local PT's in the area to get an idea of pricing and trial it for a month or 2, I have a feeling you won't be asking what the secret is for weight lifting anymore. Good luck!