Determine first the elements inside set A. Once you do, you can write the subsets of set A by set, or for it to be easier use the power set.
Example:
A=*insert braces here* 1, 2, 3*insert braces here*
Subsets:
B=*insert braces here* 1, 2, 3*insert braces here*
C=*insert braces here*1*insert braces here*
D=*insert braces here*2*insert braces here*
E=*insert braces here*3*insert braces here*
F=*insert braces here*1, 2*insert braces here*
G=*insert braces here*1, 3*insert braces here*
H=*insert braces here*2, 3*insert braces here*
I=*insert braces here* *insert braces here*
Remember, every null/empty set is a subset of every set. The set itself is also the subset of every subset.