You didn't specify which version of FileMaker you were using. The behavior is different between v11 and v12
In FileMaker 11, it used to be that if you did a click and drag, only those items that you have completely drug your mouse over (all 4 corners) were selected.
In FileMaker 12, when you click in drag, this is no longer true, any object that is in your selection area will be included without having to enclose all 4 corners in your selection area.
FM 12 Pro Advanced V3.
Lock the background objects and they will not copy. Select the object you want to lock and CtrlAltL (windows) and the object cannot be moved or copied.
This is more than a little frustrating.
I have a Tab which has a number of fields, buttons and graphics on it that I want to copy and move to another empty Tab. I locked the Tab that has the required elements. I did my select & copy but when I paste to the new empty Tab, everything gets pasted there. Why? This didn't happen in FM11 as I remember.
As MattLeach has pointed out, there was a change of behaviour in FM12; if you lasso objects on a layout, anything you touch will be selected; also, if you simply click on a tab object the tab itself and everything on it will be selected.
However, you still have direct select available. If you hold down the command key (on a Mac, equivalent on Windows) as you lasso, only the objects that you completely surround get selected (just like in FM11). So if you want to copy SOME of the fields and objects on a specific tab, just command+lasso those objects and you should find you can copy those only.