Not a judge, but here's the best I can come up with.
Witnesses: You put the Witnesses and the permanents onto the field and the non-permanents in the graveyard. Then, all the Witness ETB triggers go on the stack (in whatever order you want, choosing which cards in the graveyard you want for each one). Then, when you resolve the Witness triggers, you put the cards from the graveyard into your hand.
Land Auras: I believe you target which lands you want to enchant that are already on the battlefield and enchant them.
Sequencing: If you cast Genesis Wave, everything goes onto the battlefield
at the same time so it sees everything else entering, if that matters. All triggers will trigger at the same time, and then you get to put them on the stack in whatever order you want.
Edit: And it looks like a judge already page-sniped me, but it's good that what I said is valid.