It is your turn, which cards should you ask for, and in which order (assuming you get another turn) in the following three situations?
Please give explanation/logic/reasoning/maths behind your choice.

1. You hold 566777 and have not asked for any of these ranks yet.

2. You hold JQQKKK and have previously asked for all of these ranks. Your opponent may have either given you some of above, or told you to 'go fish'; makes no difference either way.

3. You hold 234455666777 and have previously asked for each rank of the even numbers, but none of the odd numbers.