tell people what to expect in terms of timings and meals etc when you send out the invites - so they can plan, esp if they have kids
make sure non-alcoholic drinks are available and obvious - have downed a mouthful of disgusting bucks fizz thinking I was getting orange juice, too many times at weddings!
if there are going to be speeches, set a time limit! My dad stood up and said "Thank you all very much for coming. I would like to propose a toast to the bride and groom" for which he got a round of grateful applause.
Plates of nice biscuits when you arrive at the reception - cheaper than canapes, fill a hole. I think people are positively grateful for informality at weddings.
receiving lines are good for you to get to talk to everyone but grim for all the people queuing for ages - just make sure you make your way around the room
we didn't do seating arrangements, just let everyone sit with who they wanted - seemed to work. Mind you it was in the Rugby club hall with long trestle tables so that helped!
Favours? Nobody will notice or care.
I asked several friends to take photos with their own cameras and paid for the prints. Other friends have found that you get hundreds of really awful photos from disposable cameras, because everyone fools around with them and gives them to their kids to use.
Don't spend more than you can afford. The memories of your wedding day that you treasure most are not going to be the bits your paid for.