I believe it should all go the same direction. My DH and I laid our laminate flooring several years ago and that's what the sales people advised. If you change direction you will need a trim strip or something to cover the transition (unless techniques have changed since we did ours).

Donna

Across the joists is the correct orientation.

It should run horizontally. On top of the "subfloor". From what I hear, IMHO.
Casey

Personally, I would lay it in the direction you want in the bigger area, and keep that same direction everywhere.

If you choose to change direction, you do not need "a trim strip or something to cover the transition" unless you have a terrible installer. I have changed direction in rooms vs hallways. You need to specially cut a groove in the first piece, or cut a special tongue piece to fit the 2 grooves together, depending on the direction you are installing. You just need to make the ends of one piece fit into the side of the next piece, and it takes a bit of conscious joinery. If your installer is some joe with no carpentry skills, he might just leave a gap and cover it with a speed bump. Don't let that guy install your floors.

As for the direction of the joists, this was true back in the day, when you wouldn't have subfloor, or your subfloor would be in planks, so you'd have to be sure to run the planks in the opposite direction of whatever was underneath them. Is there a reason to keep doing that nowadays, when most people have 4x8 sheets of plywood as their subfloor?

Most people do not have plywood subfloors. They have OSB. And builders are noted for not building one iota above code minimum unless forced to. (They often do not use joists strong enough to support tile without significant reinforcement.) Which means that you often will get some deflection in your floors. AKA bounce and movement. Wood floors will be a stronger installation across the joists, and will deflect less. If you had your builder upgrade the joist height, spacing, or subfloor material, that may be unnecessary. But, most people pay far more attention to the pretty covering over the structure than the actual structure itself. Probably only 1/8 of the people who build even know what their joist height, spacing, and span, as well as the subfloor material might even be. Yet that is critical knowledge when selecting the pretty stuff that will cover those bones.

We recently had hardwood (3 1/2 inch wide white oak planks, site-finished) installed in living room, dining room, and hallway. Our installer was adamant that it be laid perpendicular to the joists. Since he was the expert, we trusted his judgement.

I had a similar situation and chose to do a direction change. I'm on a slab so there were no joists to worry about.

I could've gone either way, really. Probably keeping one direction is better, but I think mine turned out fine too.

on the diagonal, just because I like the way it looks.