How do you return to your ship in Starbound?

Solution 1:

In the top-right of your screen, there is a button to teleport back to the ship. It's right above the Quests button.

Image of the button

Note that it will only be available while on the surface of the planet, outdoors. Going underground will make it vanish, like this:

Image of the buttons being missing

Note that the definition of "underground" is a bit crude. All you need to have teleporting available is that:

There is no background wall on the square your head is occupying
You haven't gone too far down.

This means that, for example, in the following image, I am able to teleport:

Image of me decidedly underground

Even though I'm underground, with ceilings and background everywhere, because I'm not too far down, and because I've punched out the one square of background where my head is, teleporting is possible.

Lastly, while you are onboard your ship, the same button will change to allow you to teleport back down to the surface at any time, without having to actually walk over to the teleporter. It's not much, but it's handy.

Picture of the Teleport to Planet button

1.0 and later

If you are playing on the "casual" difficulty, you can use the button to beam up to your ship anytime, except when you are in dungeons. This means even on Outpost, where on older versions you were obligated to use the teleporters to get back to your ship. If you're playing on the "survival" or higher difficulties, the functionality is the same as described earlier.

Solution 2:

On the right side of the screen, the second button from the bottom (looks like an upwards arrow) will take you to your ship. Note that it only appears when above ground AND you are not in front of background blocks. This includes blocks in your house as well.

Solution 3:

When you're on the surface, an icon will appear in the top right corner. It looks like a circle with an arrow coming up from it. Click on that icon, and you will teleport up to your ship.

Note: On the surface means nothing between you and the sky, and no background behind you.

Solution 4:

In addition, if you're somewhere deep underground, you can just quit to main menu and come in again. You'll appear at your spaceship.