Hi Leon8200
load up alsamixer then hit F6 key to select your desired sound card, always select then hit enter (if you have more than one we'll get to that later).
Then check the function of all the slider volume controls set then say at 50%, see if any are muted especially the Master volume (indicated by " MM " in the box beneath the volume slider). Use the arrow keys to select a control then the " m " key to unmute any which indicate " MM " which should change to 00. The arrow keys may bring into view any controls which are off screen (out of sight usually to the right of the window).
move the sliders up a little until you can hear music (assuming you're playing something) A word of caution, never select 100% volume on any control, I've heard of damage to the hardware or your ear's can occur :p
This is a most basic method, but is good to get things started
How we doing now?