Exercise is kind of personal / varies depending on what you like to do. For me there was actually 2 pieces to improving my exercise routine:

1. Starting a habit of exercise.

This was a necessary first step if you don't already have exercise as a part of your regular life. For me, my goal was just to just arrive at the gym every day. I didn't workout every day; sometimes I straight up walked in, walked out, and went home (or used the sauna haha). But inevitably, I ended up working out a good amount, and start making it a part of my routine. Basically, my recommendation is not to try and optimize anything at first; just try to make it as easy as possible to succeed at habit-building. Find some kind of activity that is fun and make it a regular part of your schedule. Social sports activities are also great if you can get peer-pressured :P

2. Making exercise more effective

Once I was training regularly, I found things I wanted to improve, and so I started to create goals. I'm a rock-climber, so there are certain things that I want to do to improve that. Once I started working on those goals, I wanted to improve the effectiveness of my gym time. At a certain point, I made an actual daily schedule of what exercises I do. If you want to improve the quality of your exercise, putting in the effort to make an actual workout schedule is the biggest thing you can do imo. It doesn't even matter if it is a "good" plan. Just actually following the plan, you will find the areas you can fix/improve that plan.

With my current routine, I have a 10 minute warmup mobility routine every morning, climb 3 days a week, workout 3 days a week (sometimes at the gym, sometimes at a nearby calisthenics park), and avoid the gym for 1 day a week.

But it started by just trying to arrive at the gym every day.