My world is created. It's different every time.
Far to the north of my fortress, over a particularly rough mountain, there is an enormous canyon, and beyond that a bit of plateau that ends in a massive cliff. I struggled to descend that cliff without falling off, but once I made it down, I found a vast plain and then a new sea, where I picked up some water and created a very impressive waterfall over that cliff. I thought I might find a sea route there. Instead I ended up mapping all this coast and never coming close. Arrows at the top show roughly some points along the usual land route there.
I needed to find my way around the world in Minecraft. Clearly the thing I need is a map. There are few mapping programs for Linux, and I haven't bother trying any yet. Instead I decided to get in a boat and map the coast, just like the old days, using only the sun and moon and the very grid of the world as a reference. I followed the coast for two days, stopping twice to mine coal at night, and then mapped the coast on my way back. The scale is not perfect, and there are a lot of islands missing because I didn't venture far from the coast. That's my fortress at the top right, and there is still a lot more coast to map to the South and East.
East is at the top for a couple of reasons. First, magnetism doesn't matter in this world. There is a compass, and it always points to your spawn point, which for me is just a bit SE of my fortress. But it's still possible to tell directions because the sun and moon always rise in the east and set in the west, and the clouds always drift north. But the day/night cycle is by far the most important thing (less for me because I'm playing in Peaceful mode at the moment).