Lemon Tree

I have my Lemon tree, not very big, 2-3 feet in height
Its given me fruit all through the winter, even now there is fruit growing on it
Gets watered with rainwater and general plant fertilizer when I remember
But there are some branches and twigs on it that has no leaves
I'd like to prune it, but I have never pruned it before, it seems to just get on with it's self
IF I do prune it, where do I start ?

There is plenty of light and air getting through the tree, its just the sort of twiggy bits I'd like to know what to trim out
The twigs that have no leaves on

Oh, well, just have to do what I can