You could always click on the column heading "preparer name" to have it sort by preparer.

Do you mean this thing, launched via HomeBase -> Query?

The options in the value drop down should reflect all the values it sees for the given field.  Say you're filtering on "Client Status".. if all your returns are either "Transferred" or "Interview" then those will be the only two options that show up in the drop down. 

If you know you have values for those fields and they are not showing up.. might be a program error.