I have recommend Flamerobin as Firebird Management Tool in my earlier post, because it is free and light weighted. Recently I found another tool called EMS SQL Manager for InterBase/Firebird. It is a commercial software which has a free version. The free version does not have an expire date, but it will have a splash screen that halt the program for a while during start up. However I do believe the wait is worth because it has a bunch of features that every developer want.
To use EMS SQL Manager (I download the stand alone version, which no need for installation), you will need Firebird Access Library that within Firebird binary folder. Depend on what type of server you want to connect, for server based Firebird, you need to configure the Manager where fbclient.dll located. And for embedded Firebird, you need to locate where is fbembed.dll.
Other than Firebird, there are tools for other database such as: