By Frozenfire, from the original post Using SQLite Database in Unity3D 4.3.3f. However this guide is for Windows users.
1. Download a Precompiled DLL of SQLite http://www.sqlite.org/download.html
2. Move the sqlite3.dll and sqlite3.def to Assets/Plugins in your unity project
3. Download SQLite Browser http://sourceforge.net/projects/sqlitebrowser/
4. Create a database in your Assets/ folder in your unity project with SQLite broswer
5. Copy System.Data.dll and Mono.Data.Sqlite.dll from C:Program Files (x86)UnityEditorDataMonolibmono2.0 and paste them in your Assets/ folder in your unity project
6. Access the database as above, only where “/GameMaster” is put “/YourDbName”. Note if you did this correctly MonoDevelop should have all of the methods when you type reader.
7. When building you must copy your database file to the folder that automatically is created called yourProject_Data wherever you saved the executable.