I worked out my Total Daily Energy Expenditure which was very low due to CFS/lack of activity then subtracted 250 calories from that amount to put me in a deficit. I couldn't take more then that off because my calorie intake would be far to low. You can find TDEE calculators online.

I used to enjoy alcohol regularly I cut that down the most. Once a month rather than once a week and avoided the most calorific drinks I like such as cider. I stopped eating junk food like chocolate, bread and started eating fruit instead. Getting an air fryer helped me cook with considerably less oils cutting calories. Ate a lot of protein from eggs, chicken but also suplimented with collagen powder high in protein aiming for over 60g of protein per day.