During Navratri it is very auspicious to light the Akhand Jyoti in the home. It brings happiness and prosperity for the worshiper. In Sukand Puran it is mentioned that among the light of fire, the light of the Sun, the light of the Moon, this lamp (Akhand Jyoti) is the best of lights. The light from the Akhand Jyoti enlightened the human body and mind and increases the concentration. Due to increased concentration the worshiping of almighty becomes more effective.
How to light Akhand Jyoti:
Use a big enough diya made from metals preferably gold or Copper which can hold enough ghee for at least 24 hours. The bigger size deepak will be very easy to maintain daily. Gold and copper are auspicious for dev upasana.Silver diyas should be avoided in Dev/Devi upasana as it is fit for Pitr puja only. An earthen diya is also good but for Akhand Jyoti it is not safe and can cause oil seepage.
Light Akhand Jyoti on the first Navratri in the morning and also keep a copper vessel (Kalash) full of water along with it. After lighting the Akhand Jyoti, Place it on a ashtadal kamal ( a diagram representing an 8 petalled lotus) or a triangle made with sindoor and ganga jal paste. This you can make on a copper plate or a piece of new cloth or bhojpatra.
After placing the deepak, worship it with uncooked rice (akshat), sindoor, kumkum , paan leaves and beetle nut and some dakshina and pray that, Hey Deep Jyoti, Please remain enlightened till the time I complete my Navratri puja.
Mantra for Devi Puja:
Use the following Mantra and recite it with a Mala followed by durga stuti path and aarti of durga ma. You may recite 1,3,5,9 Malas as per the time availability.
Normally a cotton wick is used, but for Lakshmi Puja a wick made up of Red Mauli is preferable. Ghee or Til Oil can be used. If You use Ghee, then place the deepak on the right hand side of Devi and if you use Til oil then place it on the left hand of Devi.
Mustard oil can also be used, but this is used only in tamsic pujas to create problems for your enemies and such puja should be avoided.
How to Maintain the Akhand jyoti:
Once or twice a day, you will need to check the oil and the wick also. Before this light a small diya with the Main Diya and then you adjust the wick and oil in the Main Deepak. After you are done, extinguish the small diya by dripping oil/ghee. Do not blow air to extinguish it.
Significance of Akhand Jyoti:
Japa done in front of a akhand jyoti is 1000 times more effective. Deities like ganesha, hanuman, bhairav and Devi are pleased when worshipped in front of a Jyoti. Akhand Deepak represents your unshakable and unflickering faith in your Isht Devta.
Extinguishing of akhand deepak is considered inauspicious, so be careful in maintaining it. This is an omen that there are upcoming problems. If this happens, light the diya again and do the puja again and increase the count of japa you regularly do to give you strength to fight with the upcoming problem.