Basic Fills from a textbook

8beat (8th note, half bar)

C: crash cymbal
h: hi hat
s: snare
b: bass drum
H: high tom
M: middle tom
F: Floor tom 
-: rest (or tie)

(Example 8 beat pattern. Any pattern is fine.)

C h h h h h h h | h h h h (fill in)|  
    s       s   |     s
b       b       | b

Practice fill-in at the end of every 2 bars or 4 bars.
Try all the following fills and practice difficult ones repeatedly.

(in 8th note)
01) s s s s 

02) s s s s
    F F F F

03) s H M F

04) s s H -

05) - s - s

06) s s - s

07) - s s s

08) s - - s

09) - H M F

10) - s H F

11) - s s -
    - F F -

12) s - s s
    F - - -

8beat 2(16th note, half bar)

C h h h  h h h h | h h h h (fill in)|  
    s        s   |     s
b        b b     | b

(in 16th notes, *: was difficult for me. Spaces are just for readability)

01) s - s -  s s s s
02) s s s s  s s s s
03) s - s s  s s s -
04) s s s -  s - s s
05) s - s s  s - s -
*06) s s - s  s s s s 
07) s s s s  s s s -
08) s - s -  s - s s
09) s s s -  s s s -
10) s s - s  s - s s
11) s s s -  s - s -
12) s s - s  s s s -

(toms)
13) s - s -  s s H-
14) s s H -  M M F-
*15) s s H H  M M F F
16) H - M -  F - s s
17) H H H H  F F F -
18) s s H -  M - s s
19) s s H -  M - s s
20) H - s s  s s F -

8beat 2(16th note, one bar)

C h h h h h h h | h h h h (fill in)|  
    s       s   |     s
b b     b b     | b b

01) s s s s  s s s s  s s s s  s s s s
02) s - s s  s - s s  s - s s  s s s -
03) s s s s  s - s s  s s s -  s s s s
04) s - s s  s s s -  s s - s  s s s -
05) s s - s  s s - s  s - s -  s s s s
06) s s s -  s s s -  s s s s  s s s -
07) s - s -  s - s -  s s s s  s - s s
08) s - s s  s s s s  s s s s  s - s - 

(toms)
09) s s s s  H H H H  M M M M  F F F -
10) s s s -  H H H -  M M M -  F F F -
11) s - s s  H H H -  M M - M  F F F -
12) s - s -  H H - H  M M - M  F - F -
13) H - H -  s s s -  H H M M  F F F - 
14) s s s s  s - H H  H H H -  F F F F
15) s - s -  s - s -  s s H H  M M F -
16) H - s s  s s F -  H H M M  F F F -

8beat 3(fills with bass drum, half bar)

fill in every two bars or 4 bars

(in 8th note)
01)- - C -
   s - s - 
   - b - - 

02)- - s - 
   b b - b

03) s - s -
    - b - b

04) - s s -
    b - - b

05) s - - -
    - b - -

(in 16th note)
06) s - - -  s s H -
    - - b -  - - - -

07) s s s s  s - - -
    - - - -  - - b -

08) C - - -  C - - -
    s - - -  s - - - 
    - - b -  - - - -

8beat 3(fills with bass drum, one bar)

(in 8th note)
01) s - - s  - - s -
    - b b -  b b - b

02) H H - M  M - F -
    - - b -  - b - b

(in 16th note)
03) s s - -  - - s s  - - - -  s - - -
    - - b -  b - - -  b - b -  - - b -

04) - - s -  s - - -  s s H -  s - - -
    b - - -  - - b -  - - - -  - - b -
END