Visualizing Intervals and Mnemonics
Every Good Boy Does FIne
I'll pretend this is a standard treble clef staff. A treble clef has lines with the notes EGBDF. I remember this with "Every Good Boy Does Fine" The names of the spaces spell FACE. This is sometimes called the G clef because the curl of the treble clef wraps around the G line.
A bass clef has lines with notes GBDFA, spaces are ACEG. Good Boys Do Fine Always and All Cows Eat Grass. This is sometimes called the F clef because the two dots on the bass clef mark the F line.
Anyway, it occurred to me that notes on any two lines together are thirds; G and B, for example. And a line and space would be seconds. Because I know the scales well, I think, "Oh, since it's the space above the G, it's G's second, A." In short, the space between two notes correlates with intervals, which makes it easier for me to read than the mnemonics.
Reading Alfred's Basic Piano Book, Level 1B, on a page discussing intervals, helped spark this insight. I'm no expert musician, I hasten to add as a disclaimer.
Hope this helps! Practice hard and let me know if you have any questions!