i am yet looking for a standard format, but i believe there is none. it is one of the most creative parts of the report. however, i found two ways of writing it.
first, the informal way. here you start with saying something different like " geez, i never realized how freaking long this project would be". then you go on thanking people, starting from those who helped you the most. finish with something different again like " ... glad i could finish this".
second, the formal way. start with "i take this opportunity with great pleasure to thank ........."etc. end with " ....... will serve the mankind at its best" etc. choose people in order of their posts and importance, like project guide, principle, director, end with family, parents, keep friends in the middle and add some dry humour there.
in both cases, preferably mention exactly what help they rendered, its not compulsory though. write full sentences, NEVER list people with bullets, its demeaning. better write with comas.
i know it wont help much, its not helping me anyway. the best way is just to start writing like an author and THEN put it into format.
sutanu