If you're tight on money, try putting a compost building at the very back of your zoo, or where guests won't be able to see or smell it. It is a great moneymaker.
If you need your ZR to only go up one or 2 points, and you have a bit of money to spare, complete some research even if you don't need it. Part of your ZR is based on this, and sometimes all you need in a scenario is to complete those and it will get you over the top.
As for guests, try to make sure that wherever they are walking, they are they are seeing animals as much as possible. Happy Animals=Happy Guests
It's also a good idea to use only restaurants instead of food courts, bathrooms and trash cans don't make a good impact on guest happiness. Same thing with elephant rides. I find the best attraction seems to be the carousel.
Aeris - I would recommend not putting the boat rental or swim with dolphins. They don't seem to make alot of money, and guests are usually tired when the come out, in turn making them unhappy. You might want to put a carousel or animal theatre in instead.