There are very many methods now and it's really individual, for some people some methods are the best, and for some the same ones aren't effective at all so I can just share with my own experience and maybe some of my tips will be useful for you too.
So the most effective ones in my case were:
- avoiding too much sugar and starches in your daily menu
- eating low carb vegetables and food which is a source of fat and protein
- making your exercises regurarly (if it's a basic and not too difficult complex, then you should make them every day, if you prefer gym more,than visiting it 3–4 times a week will be ok)
- leaving one day per week for eating more carbs
- drinking water a half hour before meals
- drinking coffee/tea for boosting your metabolism
- sleeping enough every night (the lack of it is one of the strongest risk factors for weight gain)

Also it's recommended by professional doctors/trainers to check your hormones before the start or later in the process if you don't see visible results after a long time of the weight loss work. For example lack of human growth hormone often causes the weight gain and demands treating in natural or medical ways https://www.hgha.com/hgh-injections-for-sale, also high cortisol, low thyroid and testosterone are a widespread reason for too slow/inefficient weight loss.