Usually a higher voltage will make a light bulb shine brighter; but if the voltage is too high, this can also destroy the light bulb.
more battery's or a better bulb.
Increasing the amount of electrical current flowing through the bulb's filament will make it shine brighter. Additionally, using a higher wattage bulb or a bulb with a higher lumen output will also produce a brighter light.
Wipe it with cloth I guess?
change the battery
The bulb will get brighter
If the current is stronger then the bulb will be brighter.
That does not depend directly on the brightness of the bulb, it depends on the current drawn by the bulb (which depends on the efficiency of the bulb). For example an incandescent bulb will draw much more current than a much brighter CFL bulb or LED bulb. Therefor switching to an brighter LED bulb can make the battery last much longer while switching to a brighter incandescent bulb will make the battery run down quicker.
The bulb becomes brighter unless it is too much till it shot-circuits.
When you move a bulb closer to the battery in a circuit, it will receive more electrical energy as the resistance decreases. This will cause the bulb to shine brighter due to the increased flow of electrical current passing through it.
you can make it brighter by adding another battery/cell
If the voltage is appropriate, the bulb will shine.
Two batteries in series will cause the bulb to burn brighter.