I used my breath as an anchor for a while and had a good few successful WILDs doing so. I just kept my attention on the breath as it came in and out and whenever my mind wandered I brought my attention back to the breath. It’s essentially just meditation. Eventually I did become too good at keeping my attention on my breath though and it started to keep me awake. These days I use a mantra in time with my breath which I find quite effective.

When doing counting as an anchor I find counting to 10 over and over is better than counting to say 100 or more as it becomes more repetitive, more boring and harder to focus on which is kind of what you want as it helps you fall asleep quicker which is better than staying awake.