What i've learnt about IK so far:

(Using Arm Example)
- Select the Shoulder, Lower Arm and Hand Joints (not the elbow) and press 'IK Chain' - this makes the arm animate properly by just moving the end joint (Hand)

- Find the Goals that were created and put them into a new Null Object.

- Click on the new Null Object and make it appear as a sphere or circle and position where needed.

- Click on the Shoulder bone and then it's IK Tag and press 'Create Pole'

- Move the pole outward and reset the pose (in Mesh Tag)

- Move / Rotate the Pole and Null Object to animate the arm.

First Animation using my self-taught & built rigg: Here <----- Link