Dissertation acknowledgements

The acknowledgements are the only part of the dissertation where you are writing as yourself instead of the Impartial Professional Narrator. Just relax and be honest. (Yes, that can be hard, especially after so many years of writing as Impartial Professional Narrator.)

Don't worry too much about writing it the right way. Just be yourself. Of course your acknowledgements will sound trite to the average reader, but you're not writing to the average reader; you're writing to your mentors, colleagues, friends, and family, who will value the sentiment far more than the specific words.

And don't forget to send a copy of your dissertation to each of the people you acknowledge, especially your family.

I'd like to add one more point to JeffE's answer - though I have no idea how localized this is:

Over here, the "I-did-the-work-myself" declaration contains a phrase that noone but those named in the acknowledgements did help with the work. So in addition to thanking all the people whom you like to thank for moral support etc. (where forgetting someone would be impolite, but usually not have any further consequences), it is legally important not to forget anyone who helped with the work.

To mirror JeffE's answer: Your Acknowledgements section is for you. And possibly the small number of people who will actually look at your dissertation cover to cover. Write it in your own voice, and write it the way you want to write it.

For reference, this is mine, with identifying information removed:

I would like to gratefully acknowledge the guidance, support and encouragement of my doctoral advisor, Dr. Chair, and the members of my committee during my time at University, as well as Dr. Helpful for her continued mentorship and collaboration, and for logging many miles between City A, City B and City C while on my committee.

My gratitude extends to Dr. Data and Dr. AnswersMyQuestions at Nearby Institution for their enthusiasm and willingness to provide both data and clinical expertise, to Expert for references and advice about Topic and to my friends at University for many hours of mutual support, complaining and insightful discussions in the student room.

This dissertation would not have been possible without funding from the FUNDING AGENCIES.

Finally, I would like to thank the makers of Dr. Pepper and the members of the StackOverflow and CrossValidated communities for their invaluable assistance in many a late-night coding session.

Yes, it's a little flippant, but in my opinion something in a dissertation should be, and to quote the Rifleman's Creed: There are many like it, but this one is mine.