Major Key Signatures Handy Guide Theory Things   William Wieland
1. Memorize the order of sharps. ( FCGDAEB )
2. Memorize where they go. ( C sharp major )
3. step above the last sharp (the next letter) is the key.
    (The last sharp is ti.)


Key Signatures is a good explanation from musictheory.net
Key Signature Identification set to major keys is a good drill from musictheory.net