Leg training tip: Warm up both the quads and hamstrings, even on workouts where you are training only one. Quads and hams are antagonist/opposing muscle groups. For the quads to fully contract, the hamstrings have to fully extend (and vice versa). Sometimes, that feeling of not being able to get a good squeeze or tight feeling in the quads, may be because the hamstrings are not warmed up and not able to fully extend (and vice versa, of course).
As I am no longer in my 20s, I have to deal with working around sore joints (elbows, knees). Some movements like overhead tricep extensions are hard on the elbow when the weight gets heavy. The easy answer is to not lift heavy or skip those movements. The better answer is to just be smart. To do those triceps extensions, I will alternate using a moderate dumbbell and superset immediately with using bands. The approach works for me since the combination fully works that muscle group (the DB version is hardest at the bottom when the tricep is extended and the banded version is hardest at the top of the movement when the tricep contracts).