The general guidelines for setting up PCTFREE and PCTUSED are:

If the table is of

1 Mostly inserts, Set a small PCTFREE and PCTUSED as 40

2 Queue like - rows are inserted and subsequently deleted soon after- Set a small PCTFREE (5) and very small PCTUSED (10).
Example, an audit table (log table). Rows older than a month get deleted every day.

3 Randon Insert/Delete, estimate row size. Then apply the formula given below:
PCTUSED = (100 - PCTFREE - (MAX(10,(MAX_ROW_SIZE/BLOCK_SIZE)*100))
If the PCTUSED ends up -n negative, set it 1.

4 Mostly update. Estimate row expansion in %, and set it to PCTFREE and set PCTUSED as 40.

Tamilselvan