Acknowledgments for all help received during the course of a research project or academic paper should contain the full names of those being thanked, along with details about how they were of assistance. An example might read, "I am indebted to the invaluable assistance of Dr. Lee in suggesting many of my key reference texts." If acknowledging a group, all assisting individuals within that group should be thanked by name.
Those acknowledged should include anyone who provided assistance with coming up with the initial idea, with planning or execution and with supplying materials or recommending sources. They should also include outside reviewers of drafts and any funding bodies or individuals who supported the work.
Generally, acknowledgments need not adhere to the usual rigors of an academic writing style, which means that people may be thanked using a first-person voice. Even so, acknowledgments should be brief. Specific departments and publishers may have their own requirements for how to phrase them.
It is also important to note that an acknowledgment is not the same thing as a dedication. The latter's purpose is to state whose honor the project has been undertaken in, not who helped carry it out.
In most cases, the "Acknowledgments" section will be placed between the "Discussion" (conclusions) and "Literature Cited" (references or bibliography) sections. The number of the acknowledgments should usually reflect the size and duration of the work.