-)Be Confident
-)Make lot's of miners
-)Scout (yes it's important)
-)Expand excessively, and don't expand at your natural (the most natural place for you to build a second base at, usually right in front of your base) because the enemy will find them both, if they are far apart, there is a greater chance he will find only one and focus on that.
-)If you have 10 miners at your original base, and 2 at your other one, send 6 of them over, because you have been using the minerals at that main base for longer than the second, having 2 miners each  at 6 bases is better than 12 at one base because : if one dies, you still have more, and they wont run out as easy.