During kapalbhati, you just need to focus on exhalations using abdominal muscles. The action plan may be like this:
(i) First Take Deep breath in and Exhale fully - 3 Times.
(ii) Take Deep Breath in and then start exhalation strokes using abdominal muscles; initially the strokes may be upto 25-30 and later after good pracitce, the number of strokes may be increased to 60 and even beyond. This is one cycle.
(iii) Then resume first step.
(iv) Resume second step. This is second cycle.
Thus, you can do 4-5 cycles initially. However, you need to check with your physician or yoga therapist if you suffer from hypertension (high blood pressure) or cardiovascular or respiratory disorders.