There are a number of things you can do:

Backup your database; you can easily lock yourself out playing around with
these features.

Create custom menus/toolbars for use throughout your application.
Create a startup form (a main menu form if you have one) that is opened on
startup.
Use the features in Tools, Startup to
       set the startup form
       set your default menu (the custom one you made)
       disable all the checkboxes about allowing built in menus, toolbars,
changes, all special keys (this will disable the F11 key, among others)
       hide the db window (ensure the custom menu you create does not
include the Windows, Unhide item)

If you need to bypass these startup features, you can hold the shift key
down while you open the db.  If you feel that your users may use this to
bypass your settings, you can disable the shift key bypass - there's an
example in help for doing this(look for AllowBypassKey) or at
http://www.mvps.org/access/modules/mdl0011.htm
and
http://www.mvps.org/access/general/gen0040.htm

You can also create a MDE from your database, which will prevent changes to
forms, reports and modules (If you do this, be certain to keep your original
mdb in case you need to make changes).