After starting, allow the car with the dead battery to idle for several minutes, then try switching it off and restarting it to find out if it is holding charge or not: If not, you may need to replace the battery

If the battery is cracked and liquid is leaking out, do not try to jump start it  Buy another battery instead.  

If you try to jump start a battery with a crack in it, it may explode and even if it doesn't explode, it will not be able to hold an electrical charge

If you have the time and tools, try to clean off any corrosion around the terminals of the dead battery, loosen the wires from the terminals, clean them off, then re-tighten the wires to the cleaned battery posts.
Corroded posts can prevent the power from getting to and from the battery.

It is a good idea to keep a good set of jump cables in your car at all times

Make sure you don't dangle keys, loose clothing, or the jump leads in to moving parts of the engine

Never place yourself at risk whilst attempting to jump start a car