What almost worked for me last night was keeping my attention on my breathing, feeling my body relax further and get closer to sleep with each exhale, and waiting a second before inhaling. You have to do this without thinking about it too much, just calmly keep your awareness on it. Other times I've been successful by focusing on imagined movement as I let my body relax.

1) I'm not sure how to answer this one. Maybe someone else can answer it better. For me, I try to have as little free thoughts as possible, so my mind doesn't get distracted and just fall asleep.
2) I think your mind should always come back to your anchor eventually. That's what's keeping your mind awake and aware. If your mind wanders off too far, you might just fall asleep and start a non-lucid dream. That's been my experience, anyway.
3) This probably depends on the person. It is probably not necessary. But maybe you could try it a few times with visuals and and a few times without to see which works best for you.

Hope I was somewhat helpful. I'm still fairly new at this too.