I like to change up my routine a lot. Basically I do Day 1 - chest/triceps, bench, reverse grip bench, flys, some other accessory lifts and a 20 minute HIIT on the treadmill at the end. Day 2 - legs, squats, lunges, and core work and finish with 20 minute low intensity rowing at the end. Day 3- I like to do at 45 minute session of biking or running. Day 4 - back and shoulders, bent over rows, wide pull ups, military press, incline bench and a few others with 20 minute HIIT on the treadmill at the end. Day 5 - I set aside a day for deadlifts, front squats, and power cleans. I love this day because it feels almost like cardio doing power cleans and deadlifts. After a few weeks of this I'll just basically flip the order of when I do these days. Day 1 will be 5, Day 2 will be 4, and Day 3 will be in the middle again. Day 1 is usually always Monday, beginning of the week. The weekends are usually cardio. Long runs, long bike rides, or whatever I feel like doing. Most weekends I'll do 150-200 pushups (sets of 25 with about 30-45 second breaks). I'll take either Saturday or Sunday as a rest day. I probably don't give myself enough rest sometimes, I just always like to be moving.
As far as rep range, it's like a 4-5 week cycle. First week I'll do 5 sets of each exercise in the 10-12 rep range. The next week 3 or 4 sets in the 8-12 range. Next week 5x5s. Next week 3x3's really heavy. Then an all light week just to reset with about 3 sets of each exercise around 8 reps. Sometimes I skip the light week if I'm feeling good.
I'm' not sure if this is "right", but it's what I like and it keeps me in shape. I'm not a heavy guy (about 5'11" 175,180). At one point I was 215 because I was trying to bulk, but it got to the point where eating and lifting was a chore and all the fun was gone since I'm a hard gainer naturally.
If you want to gain some size, only do cardio once or twice a week no longer than 30 minutes. Most important part is diet. Consume more calories than you're burning and I always aim for a gram of protein per pound of bodyweight. No added sugars. All that good stuff.