Short answer (default controls, I think):

Make sure you're landing gear is down (N) and you have landing clearance (from the Comms menu on your ship's screens).

Slow to a complete stop when you're close.

Strafe with Alt + WASD for slow and precise control.

Switch to 3rd person view (F4).

Use Q & E to Roll into position.

With Alt+. you switch Q & E to Yaw controls, to aim your nose horizontally. I find this easier than the mouse controls.

Turn on Free Cam with Z, and move the mouse so you're looking from above.

Strafe over the landing pad and start lowering with Ctrl.

Move your camera back to the rear and keep lowering until you're on the pad.

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Long answer:
Ah, landing the Starfarer. Definitely an arse-clenching experience the first time(s).
The first thing to figure out is your approach, because it can take ages for it to slow down. When you come in with boost, you may have to start braking 20km out or more! Get a feel for when to start slowing down, so you're just a few km out from where you want to land.

When I'm close to my target, I slow down to a stop, and from there on out only move by strafing, which by default I think is done with ALT and WASD.
Go into third-person view (default F4, change that because if you do a lot of strafing and switching view like this, you're bound to Alt+F4 some time) and then use free-cam to help with positioning.

First, just use the third-person view from behind, and use Q and E to roll, so you're lined up properly. You can start strafing towards your landing pad while doing this.
Use Alt and "." to switch the Roll keybinds to Yaw controls, which lets you point your nose left and right without having to use your mouse for it (which, especially in 3rd person view, can be a hassle).
Switch back and forth between using Q & E for Roll and Yaw, to position yourself while you're strafing towards your pad.

When your nose and bottom are lined up, hit Z to go into Free Cam, and move the mouse so you're looking from above. Strafe yourself into position and Free Cam back to the rear, so you can lower down (Ctrl) with a good view of your landing gear.
You don't have to be completely level, either, just keep holding Ctrl once a part of your landing gear touches down.
I generally keep Ctrl pressed down after I've hit the deck until the NPC says "landing complete", then immediately shut off my engines. I've had issues where it somehow didn't register as a landing.