Here's a useful tip on understanding basic scales for those of you who aren't the greatest at music theory but want to start experimenting and make sure you are staying in complementary keys to your samples. First off, on any keyboard, each key (white or black) represents what is called a semi-tone.
With this in mind, depending on whether you are in a Major or Minor, the rule for determining the scale is as follows:
Major scale: Tone-Tone-Semitone-Tone-Tone-Tone-Semitone
Minor scale: Tone-Semitone-Tone-Tone-Semitone-Tone-Tone