Most important in the grand scheme of things, assuming you've got a clean, flat, dry, and sound subfloor, is where you start your first row.
Generally start on your longest run.
You'll find that walls are never square. Getting it straight/parallel to one wall often means it is angling on another wall. For aesthetics, you may want to decide which wall is most important that it be parallel to.
While you may not be doing a rectangular area, the textbook example is -
Find the midpoints of the 4 walls and snap a chalk line between the midpoints of opposite walls. Where the chalk lines cross, measure out from the intersection 3 feet one way and 4 feet the other. Mark those spots and check to see if the diagonal is 5 feet. If you lines are at right angles to one another, it will be 5 feet. If not, adjust your lines until they are squared.
Measuring larger distances is more accurate... it's better to measure 6', 8', and 10' than 3", 4", and 5".
You're not obligated to start in the middle of the room. Once you establish your base lines, you can snap perpendiculars where needed close to the wall if need be.