Try cleaning the battery terminals and cable ends real good as they might have dirt between them and not making good contact.
Possible ground issue at the taillights.
Most likely a fuse.
A bad ground wire will cause dim headlights, or will cause lights not to work.
probably the fuse is blown.
On a 1999 GEO Tracker, a bad fuse can cause the headlights and dash lights to blink. A bad voltage regulator or alternator can also cause lights to blink and flicker.
I would replace the headlight switch as Ford has had their share of these problems.
If by "dim headlights" you mean low-beams... the bulbs are bad and must be replaced.
bad headlight switch.
If you have no battery then you have no power.
They are either the wrong bulbs or one of the filaments is burned out. The bulbs should have two filaments. One is illuminated when the lights are on. The other is brighter when the brakes are used.
A mis-wiring or short circuit somewhere between the controls, fusebox and lights.
Faulty ground to the dash.