I suspect all the commercial ones will be the same price - they always are in Oxford
However, almost all (all?) the colleges will have punts, either their own ones, or ones they've rented for the whole season. If you know someone from a college, and it's not too popular a day, they should be able to book a college one for free / cheap (depends on the college)
Otherwise, a few handy tips:
- If in doubt, stay on the punt and let go of the pole. You should have a small paddle to get you back to the pole, and that way you avoid a swim...
- There are two ways to steer. One is by choosing the position of the pole when you push, one is using the pole as a rudder at the end of the stroke. Try to avoid accidentally doing the former!
- Going fast takes lots of practice, start slow!
- Balance yourself well, especially when people are moving about the punt. Try to ensure only one person moves at once, otherwise you may all end up in the water...
- Drinking while punting takes a lot of practice. Instead, have someone out of pole-drip-reach hold onto your glass. Don't put it near you, or you'll either kick it over, or water from the pole will go into it
- Watch others to see what works and doesn't
- Enjoy, it's fairly easy and very fun!