Specifically as it regards to strength training, I break the year into phases. I run a push, pull, legs for most of the off season. March/mid-April I will do a strength phase, working up to some 3RMs. Mid-April/May I move my rep ranges up to 8-12 and continue to do push, pull, legs. Then around June 1 I will transition to a push, legs, pull, legs to start focusing more on lower body and increasing the volume. Also starting to ramp up the cardio/rucking. Around Aug 1, I transition to a full body split 3x a week while putting more of the focus on the running and rucking. Structuring my training this way I feel like really keeps me from plateauing and sets me up to have the best base I can when the fall rolls around.
Heavy unilateral stuff is key in my opinion, especially as the season gets closer. I start to focus a lot more on bulgarians, reverse lunges, single leg RDLs, weighted step ups, etc. Those small stabilizer muscles get used a lot more and translates to the mountains. I also like to start mixing in more front squats. Earlier in the year, back squats, hex bar dead lifts, and heavy RDLs are my go-tos.
Core strength can’t be understated either, although it’s mentioned a lot on here. I would add that not just traditional sit ups, but focusing on rotational strength as well. Landmines are great for this. Mobility work is also something that really gets neglected despite how important it is. We all want to be doing this for as long as we can and building and maintaining good ranges of motion is crucial to that.
Lots of other good info on here.