How do I land a building precisely to connect to a techlab/reactor in Starcraft 2?

Solution 1:

The UI of Starcraft 2 should show you an outline of the building after you have hit the land command. This outline will allow you to place the building correctly.

When you invoke the land option, you will see two outlines: one where your mouse is and one beside the tech tab/reactor:

Simply move your mouse so that the outlines overlap:

Then, click the left mouse button. Your building will start flying toward the target location:

If you lined everything up correctly, it will land right beside the add-on:

Solution 2:

Have you turned grid on in options? Other than that, there's not much to do... practice maybe. I never had any problems with that, myself.

Solution 3:

When your building is lifted and selected, it will outline the optimum 'landing zone' to marry up to an un-utilized add-on. The add-on must always be on the right of a building, this is true for all buildings.

Try turning on the building options if this isn't already enabled for you (perhaps building grid?) There is still a little art in successful landing, but the guide can help a ton.

Hope this helps!