In order to make one Shamrock:
1. Blow up four green balloons with a balloon pump. Tie the tail end of each balloon into a knot as soon as you finish blowing it up. Try to make each balloon the same size.
Use a regular pump for this method, not a helium tank.
You don't have to use a balloon pump for this, but your lungs may get tired after a while.
2. Tie two balloons together by the tails in a double-knot. If you are having trouble with this, you can tie the balloons together using string instead. Repeat this step for the remaining two balloons. You should now have two balloon pairs.
3. Twist the balloon pairs together to make a clover shape. Place your first set of balloons over the second one in a cross shape. Pull the bottom two balloons upward. Pull the left one to the right, and the right one to the left. You will have something that looks like a four-leaf clover.
Alternatively, you can tie the balloons together in a cross shape with some string.