The biggest factor in planning a field trip is how much money the school has. Field trips are very expensive. Even if the place you are going is free, you almost always have to pay for a bus unless you can walk there.
The other major factor is distance- can you get there and back in one school day.
Finally, parental support is key. You need about 1 chaperone for every 3-5 students, depending on age. Younger students need more.
Planning ahead is very important for a good field trip. If possible, teachers should visit the site before and plan activities. There should also be some follow-up.
Don’t forget to schedule lunch. Having kids bring bag lunches is usually easiest, but many bus drives won’t let them eat on the bus.