Have body fat around 15% (as a man) and lift, making sure to gradually increase intensity through increased weight, sets, reps, or even just shorter rest periods between sets. Make sure to hit different muscle groups, if you have less time to go to the gym then compound movements with free weights are the most efficient but otherwise targeted isolation lifts are good to mix in.

You want to use free weights over machines as they'll train a greater range of motion and will build the smaller support muscles that can be missed with machines and will make your muscles "fuller".

For diet 1.6–2.2g of protein per kg of body weight daily and 4–7g of carbohydrates per kg of body weight. The rest of your calories should be from fat. Make sure to get amino acids, magnesium, and iron too. If you have healthy kidneys it's good to add 3-5g of creatine as a supplement daily too, it's one of the few dietary supplements that has been proven to be effective with very minimal downsides, essentially increasing the energy stored in your muscles for faster recovery and a couple extra reps so overall faster growth at the cost of some extra water retention (so make sure to drink more). Don't bother with steroids, they're more harmful than they're worth.

Aside from that rest days and 8 hours of quality sleep a day, as that's when your muscles actually grow post-training. It's not necessary to have a full rest day either if you don't want to, just don't train the same muscle groups until they've recovered, so if you did chest and triceps today (push day) do back and bicpes tomorrow (push day) and then legs the day after etc.