See nine ways...
1. Avoid speaking about your Ex to your new partner....he/she will think still you are mindful of him/ her.
2. Avoid mere and empty promises which you will never fulfill.
3. Never ever compare your current partner with your Ex...( most new relationship get spoiled by this comparative)
4. Never share your new partner's secret with your friends since this may cause great friction.
5. Show your total sacrifice to him/her
6. Always listen to his/her opinion even if it is negative... then wait until get a good way to convert it positively
7. Always try your best to make him/her a king/queen
8. Never assume his/her request.
9. Ensure you have deleted your Ex contacts completely and avoid his/her every time texts and calls
Lastly, be mature and use commonsense properly...