How Can I Help My Dyslexic Son?

First of all try to be very encouraging of your son and explain that because he has dyslexia this makes him 'special' in a positive manner.  Try to help your child with reading and writing, but at all costs avoid becoming a pushy parent.  If you are constantly putting pressure on your child to succeed and be 'better' at reading and writing, you may just scare him and he may become very insecure and this will make his problem worse.
However, praise any achievements that he makes and also try to get him involved in non-academic activities where he may do well.  This will help boost his self esteem and will help him to be confident.
Try not to scold him when he makes errors, but keep encouraging him and being patient.  It will not be easy for either of you, but many people with dyslexia can lead full, happy and very successful lives.