Your thesis work is almost done and you are extremely proud of yourself; however, you still have to accomplish an acknowledgment section. Soon-to-be graduates of all levels occasionally find themselves stuck when it comes to this part. It's necessary to express gratitude, but how and who are those people? After a long hard work on complex concepts and scientific topics, it may seem inconvenient to return to simple language. For sure, it should be an easy read, written in a decent language. This is a part of your work, so keep the section professional with all the necessary formatting. There are examples of people, who write incredibly long lists which include half of their family along with cats and dogs; however, this is not the best approach. Try to include people who made some real contribution into your work, because reading a wall of meaningless text can make readers bored or even annoyed. Limited number of personal and professional acknowledgements will do it's work.
Normally, the main person who contributes to your thesis is a research advisor, as he guides you along the tortuous road of science. However, there are some extraordinary cases, when advisor performed so poorly that the student doesn't want to include him. Still, think about it carefully. If your work was done in collaboration with several professors, include them with all the relevant titles and write full names. If you had assistants to help you with data collection and processing, list them as well. However, if you worked with a large group of people, just provide the name of assisting group.
Dissertation takes a lot of time and effort; hence, contributions to your work can be done outside of academia and work. Beloved people may inspire and support you during this stressful period. Don't include people who have nothing to do with your thesis just because you are grateful for something else: you will have enough time for gratitude later. However, if you know for sure that there is a relative or a friend who inspired you, go ahead. Remember to keep a reasonable length of your acknowledgement and to maintain an appropriate style. Some graduates get a bit carried away and depart from the plan. As always, proofread, re-check and don't forget to give yourself a pat on the back for such a great accomplishment.