Do you ever wake up in the middle of the night without an alarm or anything? I always recommend FILD, and if that first part applies to you it would probably be your best bet. If not you can work on some things like autosuggestion to wake up. FILD requires no effort during the day, barely any when you actually do it, and has a high success rate. I love this technique because it is not hard, and actually gives more concrete results, in other words, you don't have to rely on chance or luck like with DILD.