I wasn’t going to opine any further on altar servers, but a reader asked my opinion about what to do with altar girls if you have them.

First of all, it is obviously okay to have altar girls. Rome allows it. You don’t have to have them, but you may. If I went to a parish where there was a group of boy and girl altar servers, this is what I’d do:
But first the method behind the madness: the underlying principle is that in the created economy and the economy of salvation men and women are both necessary and equal, but different. St Paul says this in (I think) I Corinthians, “man is dependent on woman and woman on man.” Adam and Eve played different roles in the fall. Mary and Jesus played different roles in the plan of salvation. Women and men play different, but equal roles in the sacrament of marriage and the mystery of child bearing and family life. The liturgy should reflect all these truths. 
This means getting rid of the whole unisex mentality. The unisex mentality subtly undermines true distinctive sexuality and blurs the lines of the developing sexual awareness of both genders, and therefore doesn’t do anyone any favors. Furthermore, there is a kind of assumed uniformity to the genders in the unisex mentality which is untrue and destructive to true masculinity and femininity and only causes confusion in an already very confused society.
So I would first of all dress the boys and girls in different outfits. The cassock albs are more suitable for the female form, so I’d ask the girls to wear those and kit out the boys in cassock and surplice. In the combox Karen already spoke well about girls’ apparel. Under the cassock alb a dark skirt and white blouse, or certainly nothing that would show through and distract. Hair neatly cut or, if long, put up neatly without attention grabbing hair ornaments. Shoes should be simple black pumps. No flip flops, no glitzy high heels or sandals. Neither gender should wear distracting jewelry of any kind. Make up should not be distracting.
Then I would give them separate roles both behind the scenes and in the sanctuary. I’d ask the girls to fill ciboria, replenish the wine and water cruets, dress the chalice and perhaps help with preparation of altar hangings and vestments. I’d ask the boys to maintain the incense, thuribles, books and candles and manage any movement of furniture.
In the procession I’d have the boys carry the cross and candles and thurible. Girls would come next, before the clergy. In the sanctuary I’d have girls serve the alter, helping deacon prepare the altar and serving the water, wine, priestly ablutions and ablutions after Mass, while the boys hold the book for the priest, process with candles for the gospel, and carry the crucifix for the offertory procession.
Both boys and girls should be well trained, expected to be on time, dressed smartly and contribute fully to the liturgy.
Well that’s my two cents worth. It’s not gospel. It’s not infallible. It’s not even my own. Shoot it down if you want.