Once you get the C Major Scale in the muscle memory of your fretting hand, and the sound of each scale tone in your ears in order, you can start to mix them up a bit. Try going up three notes in the scale and then dropping down a 3rd Interval to the note you started on. Starting on C (Do), play C-D-E-C (Do-Re-Mi-Do). Practice slowly until you have it under your fingers and in your ears before moving on to the next sequence, D-E-F-D (Re-Mi-Fa-Re). Singing the solfege syllables while you do this will really help to memorize it. Think of each four-note sequence as a bit of melody. You might even hear a familiar song pop out!