I never worked out a day in my life until I was in my 40s but then mostly what I did was aerobics (high impact and step when it came along). I did lift weights a bit but found it boring. Throughout my 50s I didn't do anything and ended up weighing 250lbs. So, about three years ago I decided to try and get in shape. I began by radically changing my diet (mostly cutting out sugar and most, but not all, dairy and wheat) and walking A LOT.
A little of over two years ago, then down to 210, I decided to hire a personal trainer and work with him for a while as well as educating myself about weight lifting. Then I joined a gym and began experimenting with different routines and strategies to see what would work best for me. My main concern was doing it 'right' (for me) and wanting to (some of the time) lift as heavy as possible without injuring myself. I work out alone. I always begin by walking briskly to the gym.... about 2.5 miles... carrying a backpack with all my gear. That's my warm up
The way I do this is by using a squat (aka power) rack for a heavy limited range lifts. For example, I'll put a bench in a rack and set up the rails to hold the bar just slightly below my extended reach for a flat bench press. In furthest extended range I can now bench press close to 300lbs. There's no fear of injury because even if I drop the bar it isn't going to fall on me due to the horizontal rails. SO... I do my maximum lifts in this limited range and then take all the weights off and lower the rails one notch. Then I repeat only this time with less weight. Then I repeat the process again until I'm finally at a full range of motion.
This process works with: Squats, deadlifts (I did a quarter dl of 420lbs on Wednesday but only once; lowered the weight and did 3 sets of 8 at 380 before doing full range of motion at 200... I have to use lifting hooks for the really heavy lifts because my wrists can't hold it), bench press, incline bench press, bicep curls, lying triceps extensions, shrugs, bent over barbell row and seated overhead shoulder press. The only bad thing about this is it is time consuming to set things up for a move and then take the plates off to reposition the rails and bar, putting plates back on again. If nothing else, though, I get a workout just unracking and reracking all those plates, lol!
I do a similar thing with the cable pulldown, cable row, cable crunch and leg press/calf press... that is, contract or push with the heaviest weight I can in a limited range of motion and THEN lower the weights for multiple sets/reps at a weight I can handle in full range of motion while staying in good form.
Although I have an overall strategy, I do mix up my routines. I don't always do the 'heavy limited range' thing. If I do a heavy limited range workout with one muscle group lets say on Monday, when I hit that group again, two to four days later, I shoot for high repetitions of a much lighter weight but still to near failure. Sometimes I workout four days a week. Sometimes I'll work the same muscle group twice a day (rare but I do it occasionally). I'd like to do supersets more often but my gym is so crowded it just isn't realistic.
I almost always finish my workouts with 15 to 20 minutes of cardio using a step. It's sort of a HIIT thing for me. That is, I'll do big moves for two or three minutes and then do double-time step moves to burn out the ATP in my legs and get winded. When I hit that point of failure, I just pace around to catch my breath then go back to the big moves before hitting the double-time interval again. I repeat that three or four times. Finally I end it all by doing balance work and often (but not always, if I'm really wasted I'll take the bus) walk the 2.5 miles back home.
This all works for me
I'm seeing gains. I'd gotten down to 177lbs but am now back up to around 190 but with no more or only a little more fat than at 177. I keep records of my lifts so I can see where I'm improving and not and I take body measurements. At my age the growth is slow but it is noticeable. I can see the difference and feel it in my body. I'm concentrating mostly on my upper body and can really see it happening. I'm looking at this as a long-range process, too. At my age I figure it will take me another 3 to 5 years for me to get to my genetic potential.
Oh, I also take recovery time off three times a year. The week before I take two to four weeks off, I'll totally exhaust myself with double workouts in a day and eat like a horse. During the down-time, I continue to walk and do a lot of flexibility training and some body weight moves but nothing overly taxing. The idea is it is recovery time so when I go back I'm stronger.
Anyway, that's how I do it. I think everyone has to experiment to find what works for them and keeping accurate records and measurements is the only way to know what works and what doesn't.
ETA: Oh, and I do two aerobic step classes a week, Tuesdays and Thursdays. I always do arm work before the Tuesday class but nothing on Thursdays as it is an 'off' day for me. Usually I break it up something like this: A day: Pecs and shoulders; B day: biceps, triceps, forearms; C day: back; D day: legs. However, due to all my walking and aerobics, I only workout D every third week. So... I'm rotating A, B & C, throughout four days. So a week would look like: Monday A, Tuesday B, Wednesday C, Thursday off, Friday A and B, Saturday and Sunday off, Monday C, Tuesday B, etc. always doing B on Tuesdays and Fridays. But, if I'm doing a D leg workout that week, it is always on a Friday so that changes the cycle. Make sense?