Mangue, why do you want to prune? By doing so, there's a chance fruit won't develop. Are they too big, is that why you want to prune? Toni

Generally citrus do not require any pruning at all. When young, citrus will send out rather vigorous new branches. These will tend to give the tree a rather leggy look. Prune these back to about 6 to 8 inches. The branch will soon sprout 3 to 5 more branches from this cliped one, that will be shorter and give the tree a more compact crown and nicer look. It also helps the tree develop a stronger structure that can bear the weight of the fruit.
With older trees, I only clip out old branches that are dead (as in turned brown completely dead) or the occational branch that grows across another to keep a healty structure. Other than this, pruning is really not good for citrus.
Arthur the Date Palm guy (and small scale citrus grower)