- Don't train more than 2 consecutive days without taking a day off.
- Try to keep the lifting portion of your workout to an hour or less.
- Take a week off every 3 months or so, or implement planned deloading phases.
- Do at least one freeweight movement for push movements, pull movements, and leg exercises. Do more if at all possible.
- In general, you should workout larger muscles first. As well, perform heavier compound movements first.
- Rep range should primarily hang in the 6-12 range. However, going higher or lower on occasion is certainly a good idea. If you also value strength, then journey into the 3-6 range more frequently. Conversely, if you also value endurance, then go in the 15+ range more frequently.
- Try to balance your pressing and pulling movements. Also, try to balance your quad-dominant and hamstring-dominant lower body exercises.
2 day split examples:
Upper - Lower
(Full Body Push - Pull) Quads, Chest, Anterior & Lateral Delts, Triceps, Abs - Hamstrings, Back, Posterior Delts, Biceps, Abs
3 day split examples:
Week A: Upper - Lower - Upper / Week B: Lower - Upper - Lower
(Push - Pull - Legs) Chest, Anterior & Lateral Delts, Triceps - Back, Posterior Delts, Biceps - Legs, Calves, Abs
(Upper Horizontal - Upper Vertical - Legs) Chest, Back Thickness, Biceps - Back Width, Anterior & Lateral Delts, Triceps - Legs, Calves, Abs
4 day split examples:
Lower - Upper - Lower - Upper
Chest - Back - Legs - Delts, Arms, Abs
Week A: Push - Pull - Legs - Push / Week B: Pull - Legs - Push - Pull / Week C: Legs - Push - Pull - Legs
As you can see, there is a wide variety of viable splits, and it should be no problem to find one that fits your schedule. As long as you follow the general guidelines I laid out, or something close to them that affords you full recovery, then you can cram muscle groups together virtually however you please. The split doesn't even have to be based around a calendar week if you don't want to do it that way.