Something new - at least for me:
I've started moving large arc fleets - some 50 or 100 arcs strong. Not to colonize new planets (I'm getting close to where I can not longer expand without hitting my neighbours or moving through them), but to redistribute population. I have loads of fairly fresh colonies with low population and a bunch of old planets with overpopulation. So today the thought struck me: Why not move a ton of arcs out towards them? That also gives the border planets more steel to build defensive fleets with, so I don't have to move those out from the inner planets.
No idea yet whether it's a smart or stupid idea. I'll do a couple and see what I think of it.