Where to listen
This page assumes you know how to do a cardiovascular examination and is just going to concentrate on the chest as a reminder.
There are four principle areas to listen to the heart sounds and these correspond to where the four valves can be heard loudest
They are marked on the picture below but are more specifically...
2nd right intercostal space, the region of the aortic valve (right upper sternal border)
2nd left intercostal space, the location of the pulmonic valve (left upper sternal border)
left 4th intercostal space, the region of the tricuspid valve (left lower sternal border)
5th intercostal space, left midclavicular line to examine the mitral area, which is also the apex of the heart
So there is a 
shape in listening to the heart sounds and we can add the initials of the valves producing 
so APTM is the sequence that you need to remember or (this is the only reproducible one) Angry People Take Medicines.
When listening to the sounds it can sometimes be difficult to ascertain which is S1 and which is S2
...The gap between S1 and S2 is less than that between S2 and S1
...S1 is loudest at the left 4th intercostal space (mitral/tricuspid areas) and S2 along the 2nd R and L intercostal spaces (aortic/pulmonic areas)
...Feel the carotid pulse with your free hand to ascertain when systole is and therefore S1.
*Note: Feeling the radial pulse can confuse, as there is a slight delay between the heart beating and the pulse at the wrist*
