How can beginners start a safe and effective weightlifting routine?

If you're a complete beginner, you can start by activating your muscles by doing bodyweight exercises and then incorporating light weights into your workout routines. As a beginner, keep the weights light and focus more on your form. Building a good form, will help you lift heavy gradually in future and keep you away from injuries. You can build a routine on the basis of muscle groups to focus - push, pull, legs. Additionally, do not forget to include cardio and core workouts in between. Cardio and strength training both compliment each other. Combination of both is the key!

Initially do workouts with lesser weight,focus on the number of repeating. With the time you should increase the weight. I'm not mentioning workout split in the gender basis but what I do as female Monday = Legs, Glutes hamstring quads workout Tuesday=Back And abs Wednesday= Chest+triceps+shoulder+Abs And follow up this as it is next three days.