Learn the main riff. The main riff of "Cat Scratch Fever," which repeats through the majority of the song, including the chorus, is a simple variation on basic power chords. It can be played by fingering an A chord, as shown below, and moving the index finger to the fourth fret and then the fifth fret while strumming only the third and fourth strings (sounding the fifth and octave of the B and C power chords). On every other iteration of the riff, the notes in the second half of the figure are played in descending order.
|-----------------------------------------
|-------------------------------------------
|--2----4----5--5----2----4----5------
|--2----4----5--5----2----4----5------
|--0-------------------0------------------
|-------------------------------------------
Fig. 1
Add fills. With the main riff mastered and played at the song's regular tempo, it's possible to add the fills that round it out. At each repetition of the figure shown above, Nugent uses a simple ascending bass-note run to signal the new beginning of the riff. This is played simply on the lowest (sixth) string of the guitar as shown below in Figure 2. Figure 3 shows the bend fill used in the opening of the song, which is played by fingering two notes, on the second and third strings, and bending the note on the third string (fourth fret) with the ring finger.
|--0---3---4----|
Fig. 2
|-------
|--2---
|--4^--
Fig. 3
Learn the verse. The verse is similar to the main riff, but includes some additional chords. Instead of Figure 1, Nugent plays a slight variation on the main theme that transitions into three full chords, G, D and A. Listen to the song to hear how the rhythm of the riff changes for the verse.
|------------------------------------------------------3----2----0--------------
|------------------------------------------------------3----3----2--------------
|--2----4----2----5----2----5----2---------------0----2----2---------------
|--2----4----2----5----2----5----2---------------0----0----2---------------
|--0-------------------------------------0--3--4---2----------0----0--3--4--
|-----------------------------------------------------3----------------------------
Fig. 4
Take it to the bridge. The middle section of the song, called the bridge, consists of straight power chords. F#, C and D and fingered as shown below in Figure 5.
|-----------------------
|--10-----------7---
|--10----10----7--
|---8----10----5---
|----------8----------
Fig. 5
Solo. The solos to "Cat Scratch Fever" have been meticulously tabbed out by other artists, whose work is available online. It's also possible to simply improve the solo, since it Nugent's performance uses standard blues scales.