In simple terms: Eat plant-based foods, period. Veggies, fruits for snacks, beans, nuts, etc. Avoid processed foods other than plant foods that are minimally processed for freshness (liked canned foods).
I thought I would struggle to stop eating meat, especially chicken. After the first few days, vegetables and beans started to taste amazing! I had no idea what I've been missing all these years since meat mutes the taste of everything else.
I also avoid dairy and snack foods. I "cheat" about once every two weeks during social events, but even then I crave the healthier options. I now look at bad foods differently and I feel better than ever.
Tip: Take a one-a-day multivitamin that includes B12. When you’re getting started, get rid of all the bad food. If it's there, you'll eat it.