1. Never ever stretch a cold muscle, unless you're an elite athlete, or especially naive and stupid. Period. Dumb, dumb, and dumber. (A cold muscle is much less elastic...DUH). That's why weekend warriors get fucked up: they do everything wrongly. Cold stretches, not stength nor cardio conditioned. Wrong stretches. Etc., ad nauseam.)
2. Post workout soreness often is micro-tears in the muscle. It peaks two days after. You can lower it by "flushing" the muscle group the day after. E.g., for legs, ride a bike at log intensity for 10 minutes, and flush the muscle out. It'll make a world of difference. If you have poor to average capillarizatizion, and less recovery ability know that as you go along that should improve, given adequate calories as so on.
3. If you're getting THAT sore, there might be something else going on, or you might be lifting like a moron.
4. Empower yourself: try googling on "muscle soreness." A large number of universities have studied this in their sports science program. Organizations like The National Strength and Conditioning Association study this stuff, too. (I've been studied.)
5. Without knowing how long a person has trained, their state of health, their natural somatype, it's hard to advise them in a qualified way. Best the person study up.
6. As you go along, educate yourself, and your body makes adaptations, your recovery ability will improve. After 32 years of resistance training, I rarely get sore, even at very high levels of intensity. The human machine is begging to be pushed, but, you also have to learn to eat, rest, and utilization of periodization and peaking to your advantage. Like the idiotic notion of streching a cold muscle, you need to learn to educate yourself on sports science, and it IS science.
7. Make sure you lift weights through the FULL RANGE OF MOTION.