TvZ tips - Preventing Zerg Scouting

Early game, pre-Lair, Zerg doesn't really have a lot of good scouting options, and certainly not as good as your scan, or even your SCV, which doesn't have to contend with a Zerg wall.

So, what do you do?

• Wall in, even with supply depots + barracks is good.
• Block with an SCV if walling with 2 Barracks.
• Station some individual marines at Overlord entry points.  You'll start doing damage immediately, and your other marines can rally and kill the Overlord before it sees too much.