I'll tell you something that I have been doing for a while and it seems to be working and may work for others.
Every time I find myself looking at a woman for more time than I should, or if I find myself taking a second glance, I slap myself in the face or give myself a big pinch (yes, it hurts).
I know it sounds weird, but it serves a dual purpose: 1) It reminds me to be more careful next time, as I don't want another slap in the face. 2) It punishes me down here on earth, so that it will hopefully not need to be punished in the next world, which is much worse. As the Sefarim point out, that one who gets punishment down here doesnt get punished again for that aveira in the next world ("K'sheyesh din limata, ein din limalah - when their is judgement below, there is no judgement above").
See this article for a strong lesson in how important Shmiras Ainayim is.