There’s so much at your fingertips today, back when I was starting out I had to go out and hunt for books! I’m along the same lines of thinking as Brad. I’m an older athlete with 20+ years in my legs, but back when I was starting out I remember reading a lot of books. From this I pulled the ideas that I either liked or made sense to me and tried them - over time lots of different training methods rather than just one or two. You eventually start to get a grasp and a feel on how your body responds to the different training and stimuli and how you are recovering and progressing; over the years and decades I’ve taken the best bits of various approaches and tailored them to my needs and what my body responds best to
FWIW I have followed guides and training plans in the past for half and full marathons, but the results were usually mixed. The downside is that they’re ultimately just generic plans in which everybody is going to respond differently to. Maybe do some research into who some of the top or accomplished people are in your sport and do some digging into what works for them, then trial and error it until you start to get a feel of what’s working or not working. Again as Brad mentioned AI could be another good option, my training partner used ChatGPT to write him a training program for a 50km that we both recently raced and that worked well for him ☺