I think it will just come naturally with time. It feels pretty natural to stick at around 90 for low intensity. I find that if I am going really slow, it might drop to 70. If I put a harder effort, it climbs higher. I think just getting your legs used to riding will help them know what cadence they want to be at.

60 rpm while seated at anything more than a walking pace would feel unnatural. I might climb a few hills at 60, but I feel the excessive strain in my legs when I do that.