The very first thing is to assess your diet and make changes if necessary. I believe different people require different food to be and maintain a healthy existence. That said, I also believe that in general Whole foods, (not refined) raw, and organic are best as well. I am still refining and making changes to my diet so this is not something that has an end, but a journey.
Make slow steady changes you can live with, like giving up refined salt (if you use it) and use only unrefined. Then maybe give up unhealthy fats (even those found in processed foods) and exchange them for healthy fats. Then maybe give up any artificial or refined sweeteners. You get the idea...
Once you do this and make the changes lifetime habits the cleanses will produce much better and profound results.