Recently we weren't able to book any speciality restaurants until on board (at which point you can use your OBC). Freedom dining is available as are wine packages (these I believe you can book beforehand but would need to wait until you were on board if wishing to use your OBC for it). Just to let you know that if you have some of a bottle left over at the end of dinner, they will no longer store this for you until the next evening - you can take it to your cabin (to drink or bring it the next evening for dinner) or drink it in the bars/theatre.