If it is still a year away you don't HAVE to ask anything, they should show you round and tell you 'how it all works'. BUT - some schools do this better than others (as in all things educational).
So, if you WANT to ask, and appear knowledgeable, try:
What Phonics scheme used?
Are ALL early scheme books phonically decode-able?
Is there a library; how often used by Reception class?
What 'learning through play' activities in Reception?
How much PE, games and physical activities?
Break and lunch time arrangements.
Computers, white-boards, and other ICT 'tech' in classrooms/computer suite.
What art, craft, construction toys in classroom?
Music, drama, dance etc.
Lunch time and after school activities or clubs? (Though personally I think a day in Reception is enough for some kids, and clubs can wait for subsequent years.)
Oh! and observe if the children, teachers, TAs, 'dinner ladies' (MTAs), all look happy, and displays are attractive, and pots of pencils are SHARP! (You would never believe how many children are expected to learn to write with totally blunt pencils!)
Some of this will vary a lot according to the size of the school.
(If you don't understand any of their replies, come back to me! Also, I don't suggest you ask ALL of the above!)
Hope you enjoy it!
Now retired, I was a TA (male) 25 years in primary schools, so Education changed considerably during that time.