How to pick weight and reps: progressive overload, estimating your 1RM without testing it, rep ranges by goal, rest and frequency, and a sample week.
Muscles grow and get stronger because the work was slightly harder than last time. Repeat the same weight for the same reps and progress stops once the body adapts. Adding weight, adding reps, adding a set, or shortening rest all count. Making the work gradually harder is what a programme actually is.
Your one-rep max is the most you can lift once, and it anchors your training loads. Actually attempting a true maximum is risky for beginners, so it is usually estimated from a comfortable weight and the reps you managed. If 60kg was a hard set of ten, your max is roughly around 80kg. Estimates grow less accurate as reps increase, so calculating from a set of roughly ten reps or fewer is more reliable.
The common ranges differ by what you want. The boundaries are not sharp, and beginners improve across all of them.
Training a muscle group about twice a week generally beats once. Rest between sets grows with the load: two to three minutes for heavy strength work, one to two minutes when training for size is common. Cutting rest too short means you cannot handle the weight on the next set, which reduces the stimulus rather than raising it. If a muscle group is still very sore, give it another day off or turn the session into light-weight technique practice.
The easiest way to apply progressive overload is to raise reps first and weight later. If you pick a range of 8 to 12, keep adding reps at your starting weight until you can do 12 on every set, then go up one step in weight and start again from 8. That removes the guesswork about when to add weight. A training log is essential for this.
For beginners, full-body sessions two or three times a week are more efficient than complex splits. One lower-body, one push and one pull exercise per session hits each area two or three times a week, meeting the guideline above naturally. If your schedule is tight, two days such as Monday and Thursday are plenty when done consistently. After a few months, when sessions grow long, you can consider moving to an upper/lower split. Whatever the structure, give a muscle group at least a day of rest after working it hard.
Common strength-training mistakes are pushing every set to failure, switching programmes as soon as progress stalls, and training only the parts you enjoy. Taking every set to the point where you cannot do another rep builds fatigue that lowers the quality of the next session, so leave one or two reps in reserve on most sets. Stick with a programme for at least several weeks before judging it. Training only chest and arms while skipping back and legs throws your body out of balance and strains the shoulders and lower back. If you have high blood pressure or heart disease, holding your breath under heavy loads can be dangerous, so consult a medical professional before you start.
If your form collapses on the last rep or two, the weight is early for you. Movements loading the lower back are especially unforgiving when repeated with broken form. Adding weight more slowly than you would like is fine. Pain felt in a joint, or soreness that lingers for days, points at how you are training rather than how much.