Writing a masters or doctoral thesis to summarize several years of work is challenging. Here are a few points to consider:

	Reader: Filing a thesis is a degree requirement, but really it is written for a reader. Be considerate to this reader, giving him all the information he needs to appreciate and build on your work. At the same time be concise as the reader probably is in a hurry - just like you.
	Scope: Focus on your contributions, not the field at large. Many theses contain a very large tutorial component, while the actual work is only touched on. There is no set length for a good thesis, but 5 pages are usually not sufficient to clearly describe your work, and 50 or more pages of introductory material will deter most readers.
	Completeness: Give all information needed to recreate your work. Often only the general design procedure and perhaps a textbook equation are included, but actual data is missing. Your contribution is not only finding the equation, but also applying it, so document the entire process.
	Conclusion: Draw conclusions from your results, explain why something is important (or not), and rank considerations in order of importance. This applies to every topic, chapter, and the complete thesis. Be careful, though, not to extend your conclusions too far and state limitations. Your solution may be the best in a particular situation but not necessarily always.
	Language: Incorrect language makes the most interesting thesis unreadable. Run the spell checker and proofread everything.
	Format: Neatness counts … again since this improves readability. But do not waste your time with unnecessary frills of modern word-processors.