Isn't it gorgeous? I have a whole stash from a trip to London when I was pregnant with my firstborn, and it took me almost 7 years to cut into it!
I don't know what the "right" answer is, but I pre-wash and tumble dry before cutting; use good quality cotton thread like mettler or aurifil; use lots of pins when sewing because it's slickery stuff; and machine-wash delicate, tumble dry low for the finished garment. Because it's such a fine weave, I think a french seam finish is especially gorgeous, but I've also serged seam allowances together and it's turned out just fine.
I will add that the dresses and skirts I've made with Liberty of London lawn are especially sheer, and would probably have turned out better if lined or underlined with cotton batiste.
Hope this encourages you to cut in!