There is no trick to it…..burn more calories than you consume.
I have found that it really has to be an attitude change…you can’t think of it as a diet (which sounds transient or temporary). You might find it easier to eliminate things over time. For example, eliminate/limit booze and sugared pop/soda. Then eliminate/limit candy/sweets etc.
Try to have good foods available for snacking (grapes, bananas, etc.).
Get moving. Exercise. Start by commiting to taking a walk each day.