Hi Neko
1. I concentrate on the warm/cool of the breath in my nostrils, watching it as one continuous, smooth sensation. When I notice my mind wandering from the breath, I note "thinking" and return to the breath.
Based on experimentation, I've developed this method to start (only if I am having a hard time concentrating to start out with)
I count "1" for the outbreath, "2" for the inbreath, so on up to 10.
Then I count "1" for out-in, "2" for out-in, up to 10.
Then "1" for out-in-out, "2" for in-out-in. Up to 10. Then, four half-breaths per number. Finally, five half-breaths per number.
Then I am able to stay with the breath without counting for a while (for me, this is probably 30 seconds to 2 minutes). Visual distractions may blip in for a fraction of a second, but I'm able to stay on the breath. Eventually though, the blips grow longer, and one of them might hook me and I'm lost.
2. What I wrote above is a best-case scenario. A visual distraction will just flash in and out for 0.2-3 seconds (ish), but I'm more grounded on the breath. But if I get "hooked" by a distraction, it's more like I'm under control of the thought, not even recalling my purpose for sitting.
3. Tough one. I've posted this question myself here, everyone seems to have different answers. I think I read Ingram wrote "you'll know it when you get there", so I'm probably not there. Some have said it's when staying with the breath is easy and effortless. I might get this for 5-10 breaths at best. I read something like one should work up to sustaining it for an hour, before having a base to go onto vipassana or jhanas. For me, even ten minutes of staying with the breath without getting "hooked" would be a great accomplishment.
4. Cool you are a go player

You know when you get into a fight on a corner of the board and you are just reacting impulsively, often in gote. Or in sente against an opponent during a close fight. In other words, not big-picture strategic thinking, but impulsive reactionary moves that might happen on a blitz game. When you're in atari, get out of it. Then they'll do that. Then I'll do this. Then they'll do that. Then I'll do this, and so on. Varies from 1 second to 15 seconds, breath is faintly in the background. Decided today to stop playing, at least for a while.
5. I feel any effort to ignore it only strengthens these distractions. No vows taken, so perhaps ending it would help. So far I feel fantasies are a very consistent kind of distraction regardless my lifestyle.
So far the main advice here seems is to relax, though I'm concerned if my concentration is less laser-focused on the continuousness of the breath, the more vulnerable I'll be to distraction. I'll give it a go though.
What are your standards for access concentration?