Once a child has developed good gross and fine motor skills and control, through play and drawing, as well as being able to produce the shapes and movements of the pencil to create the range of pre-handwriting patterns, they are ready to start forming letters.
Our personal view would be to start by focusing on lower case letters.
Learning to write their name is a very important skill for your child to learn. As adults we have an important role to play in helping them to write their name correctly. Always use a capital letter for the first letter of their name then follow it with lower case letters. You can explain that as it is their name (noun) it starts with a capital letter because it is an important word which we want to standout. Seeing their name written down gives young children so much pleasure; they really enjoy watching you write their name for them and are always very proud when they can write it for themselves.
We would therefore recommend teaching lower case letters and the capital letter of your child’s name first. As they master the lower case letters introduce the remainder of the capital letters. It is important that both are taught so that your child can develop a speedy, fluid and legible handwriting style.