Obviously, any subject relating to what you want to study is a good one to pick.
They will probably like you to have English too, possibly maths (though that may not be as important, as English and History are both more essay-based).
A modern language always looks good too.
Personal statement is important. I think they look for people who are smart but also have outside interests aside from studying. Maybe you play a musical instrument or are learning a language. Or you have done community service or some projects that may be related to what you want to study? Always good to have things that relate to your subject, to show your passion for it. I cannot remember what I wrote in mine anymore.
Sport always looks good too. They seem to like well-rounded candidates, people who can offer the university something maybe.
I don't know. Good Luck though! Maybe some of that was helpful.