Hakim al-Umma Mawlana Ashraf Ali Thanvi (Allah have mercy on him) recommended following tips for waking up early;
1. Eating less at dinner
2. Eating dinner earlier (ideally before esha)
3. Drinking less water (in evening)
4. Reciting the last 4 veses of surah Kahaf (18:107-110) once (at bed-time).
Basair Hakeemul Ummat page 562
Also, to have a sincere intention for this and make dua (prayer) asking for Allah’s help to arise at the specific intended time.
Set multiple alarms. One of them in a loud table clock kept at a distance from bed. This is to ensure that you have to get out of the bed to switch it off.