Major scales are the most important piano scales: firstly, because they are very common and, secondly, because they are fundamental to understand keys. If you hear someone mention that a piano sonata by the composer and pianist Franz Schubert is played in A Major, it means that it depends on the A Scale.
You can scroll down and see illustrations of all Major scales, further down you will see an overview with all the notes and the intervals, semi-tones, and finally the formula of the Major Scale. This theory helps you learn the concepts and memorizing it easier. See also Major scales exercises and arpeggios.
Uplifting trance is generally uses major chords. Every note in a diatonic scale can be harmonically supported by major chords.
A lot of uplifting trance uses minor chords as the first chord of a progression, though. VI to I is very common, since they have two common notes.
A typical 8 bar progression that could be VI-I-V-IV. It flows very nicely since most of the notes are shared between chords and it allows for some very nice bass patterns.
Especially VI to I, as you can keep the third in the bass until you want some powerful movement, then you can lower the bass to the tonic for the I chord.
That creates a very powerful uplifting sound if you do it correctly. This is a great example: http://www.youtube.com/watch?v=D756-LDqDoM
It’s done quite a bit with trance, but not always with VI to I.
Always start with the melody and fill the harmonies in according to theory.
Close related to the Major Scales are these arpeggios based on Major triads (three-note chords).
Arpeggios are for example used for melody lines and solos. The pattern shown in the diagrams below can be played all over the keyboard. Arpeggios are similar to scales, but could be seen as more melodic and more colorful.