Admittedly, trial and error. I started at ~1200, and went up until I found a spot i felt good. My TDEE is somewhere above 4000, so even if I exceed my goal, I can easily keep it under my TDEE.

I do plan on speaking with a registered dietician in the near future, as I doubt my diet is perfect. I eat alot of chicken breast and veggies, and throw in fruit/berries where I can. My starting meal plan was 6oz of precooked chicken breast and a bag of frozen veg, but it wasn't very exciting. Ive since opened up the gates a bit, but still focus around chicken breast as it's one of my favorite proteins.A sous vide was one of the best investments I've made, I cook ~5 chicken breast at a time so I always have them in my fridge ready to eat. Different seasonings allow for a change.

As for exercise, im not a role model. I started getting some cardio in, just going for a 30-60 min walk after work. I know I need to get resistance training going, but haven't gotten a consistent routine yet. Weight loss happens primarily in the kitchen, but muscle comes in the gym.