The Dedication is usually one paragraph or two paragraphs sitting on an otherwise empty page in the beginning section of your thesis. It is basically a small Oscar Acceptance Speech in which you want to thank all those who helped you through insufferable and horrible pain of sweating out some passable text inspiring and enjoyable process of creating the work of your life. It is usually the most personal (or the only personal) part of your thesis. It is considered good manners to thank your advisor in the first place and then whoever helped you professionally. Also your parents and partner/spouse. You can go ahead with phrases like:

• I would like to (sincerely/wholeheartedly) thank my advisor/parents for his/their … (patience, support, …)
• I am grateful to … for …
• I would like to acknowledge my colleagues …
• Her/his/their patience/valuable feedback/insightful feedback/support/constant support/guidance/valuable guidance/counsel helped me with/guided me through…
• I could not have finished this thesis without …

You get the idea :)