1. Decide
on the most appropriate site for aspiration;
- The usual site for puncture in adults is the posterior superior iliac spine (PSIS).
 - This may be technically difficult in obese or immobile subjects.
 - The main advantage of this site is that a trephine biopsy can also be performed. Alternatively the sternum ( manubrium or 1st or 2nd parts of the body) can be used with care as there is a danger of perforating the inner cortical layer and damaging the underlying large blood vessels and right atrium with serious consequences.
 
2. Obtain
informed written consent; 
- The procedure (in brief) and its main adverse effects (although rare) should be explained to the patient prior to obtaining consent.
 - Pain, bleeding/haematoma formation and infection at aspiration site are the most commonly seen adverse effects, however, very rarely cause major concern.
 
3.
Positioning the patient; 
- Either left or right lateral decubitous on a bed/couch, with the dorsal surface of the patient facing the operator.
 - Hold the hips and knees flexed to a comfortable maximum – knees drawn up and tucked into chest.