I have redefined procrastination.
Upon arriving at my site, I used the reveal function immediately and found an assload of silver, flux, and no iron ores, which suited me just fine because I wanted to make some sort of fun (or Fun) goblin-murdering machine, which doubles as a goblinite processor with a magma forge handy.
Naturally, I started obsessing about laying out my entire masterpiece before I applied the first pick-strike to earth, and I got so tired of my own OCD tendencies that I decided to build outdoor housing for my dorfs, until I could make some decisions.
.... a year later the tower is seven stories tall, pushing eight, and I've got 17 dwarves comfortably housed in it, still deforesting the landscape to feed the woodcrafters. So I'll have enough dorfbucks for an anvil when the caravan swings by again.
On the flip side, I've finally resolved on my entrance design. Two pump-stack towers, one for water (to feed a very high water tower, naturally,) and one for magma, built into my gatehouse. They can be discharged individually or in various combinations, depending on how badly the visitors of the day pissed me off. A permanent causeway over a 10 z-level deep pit with spikes at the bottom should make a nice complement to a battery of ballistas firing down the incoming road, and will give the poor gobbos/elves somewhere to go when the massive pressure-washer unleashes its liquid fury.
As for megabeasts, I'm divided between setting that causeway up on supports, to be collapsed if something big and nasty comes by (followed by dumping magma into the pit, naturally, then water, to entomb mine enemy in obsidian,) or having a big chunk of rock above to drop on them, just for giggles. Perhaps both. Megabeast falls, water falls, magma falls, then rocks fall. Ah! Ha! hahahahahahaha