A good weightlifting routine combines both compound and isolation exercises. Compound exercises are those that use two or more muscle groups to complete a repetition. Examples include push-ups, pull-ups, squats, deadlifts, shoulder presses and bench presses. Isolation exercises focus on one muscle group and include biceps curls and leg extensions.
Dedicate a day of the week to each of the major muscle groups. For example: Monday, work on legs; Tuesday, shoulders and triceps; Wednesday, calves and abs; Thursday, chest; and Friday, back and biceps. Spreading out your workout like this will allow your muscles to rest and grow.
To maximize strength gains, perform compound exercises first, then isolation exercises. Make sure to do exercises that target the muscle group for the day. For example, for leg day, perform squats, leg extensions and leg presses. For shoulders and triceps, try shoulder presses, close grip bench presses and triceps extensions. For calves, do calf raises and for abs, do crunches.
Try bench presses and flyes for chest day, and pull-downs and curls for back and biceps day. Pick three to four exercises for each muscle group per day, and select weights that will allow you to perform three to five sets of eight to ten repetitions. Your weightlifting session should last no longer than 45 minutes to an hour each day.
Lastly, make sure to get a good night's sleep and include plenty of protein in your diet. Both are essential for muscle growth.