Before posting a question, "May I ask..." seems would make it more politely. I wonder what are the alternatives for that phrase? Seems "Pray, .." also do, but that sounds a bit Jane Austin?
Really, there are very few. The best alternative would probably be:
Excuse me, but could I...?
..., if you don't mind me asking?
'Excuse me, but could I please have your date of birth?'
'What kind of car do you drive, if you don't mind me asking?'