Incremental weight loss is the first principle to follow when trying to increase strength and stimulate muscle growth.
Progress can be achieved in many forms but the most common way to progress is to add more weight to the bar with each consecutive training session. The question arises: When should you add more weight and how much?

When to add weight?

The answer to this question depends in one way or another on your goal. If your main goal is to amplify the muscles and you are working within 8 to 12 repetitions, you will need to gain weight once you can do all of your working groups at 12 repetitions (the highest range) and more than 2 consecutive sessions while maintaining a strict form. You will need to modify this rule for heavy composite movements such as lethal lift and slack, though.
When you make these movements, you should consider a group of singles, doubles or trios. For example, instead of doing two or three sets of 12 repetitions, you should do 12 sets of 2-3 repetitions. You should rest for a short period of time and fully reset the shape after each repetition to avoid rushing, loss of shape and eventually, risking serious injury.

It is recommended that you start with a slightly lower weight than your target audience for many exercises. This means, instead of gaining weight and trying to stay within the 8-12 frequency range, you should try 6 replicates for a set or two. After that, you can move on to a normal bodybuilding range.
If your primary goal is muscle strength and you work within 1-6, you can shoot the top of the range for at least 3 consecutive exercises before gaining weight. Much of your strength gains will be due to neuromuscular adaptations, and the central nervous system will need more time to recover properly.

How much weight should you add?

In general, you can increase 5% on upper body movements and 10% on lower body movements, provided you maintain a strict form during exercise.