Remember Flats/Sharps For Every Key Signature

Here's a little memory trick for remembering the flats or sharps in every key signature. This is something that'll work for anyone, even little kids.

Let's start with C Major, which we know has no sharps or flats. Say the following aloud, clapping an 8th note right as you say each letter:
C, D, E, F, G, A, B, C.

Repeat this several times, clapping and saying the letters faster to challenge yourself. Only clap/speak as fast as you can without messing up.

Once you've got that down, let's try doing this with G Major, except when we say F# we're going to do that in 16th notes, so that it still fits into the 4/4 bar.
G, A, B, C, D, E, F#, G.

Now G Major has a distinct rhythm in our heads:
Clap, Clap, Clap, Clap, Clap, Clap, Clap-Clap, Clap

The goal is to associate that rhythm with G Major, to drill the location of the sharp note with the scale into our brains. After spending some time with that, continue on to F Major, which would be:

F, G, A, Bb, C, D, E, F
(Clap, Clap, Clap, Clap-Clap, Clap, Clap, Clap, Clap)

Spend time every day just clapping through each Major scale in this chart. Any sharp or flat note gets a 16th note clap. Spend time on each before moving on to the next one.

C Major: C D E F G A B C
G Major: G A B C D E F# G
F Major: F G A Bb C D E F
D Major: D E F# G A B C# D
Bb Major: Bb C D Eb F G A Bb
A Major: A B C# D E F# G# A
Eb Major: Eb F G A Bb Cb D Eb
E Major: E F# G# A B C# D# E
Ab Major: Ab Bb C Db Eb F G Ab
B Major: B C# D# E F# G# A# B
Db Major: Db Eb F Gb Ab Bb C Db
F# Major: F# G# A# B C# D# E# F#
Gb Major: Gb Ab Bb Cb Db Eb F Gb
C# Major: C# D# E# F# G# A# B# C#
Cb Major: Cb Db Eb Fb Gb Ab Bb Cb