There are many ways to produce and acquire May's Holy Water, if you are Christian the easiest way is just to go and get it from the nearest Church on the 1st of May. - Check here the Article on how to make Holy Water at home! You can watch the Video on WitchTV / YouTube for free-
Now it's time to chant! If you are Christian ask help from the Holy Ghost, if you are a Believer of the the Greek Pantheon ask help from the Goddess Hera, if a believer of Celtic Pantheon ask Brigid to aid you, if you are Hinduist ask the Goddess Ganga to bless the water, if a believer of the Egyptian ask Isis to bless you, generally whoever you feel is most suitable to cleanse and protect. You can Also call the four Archangels of the East - Raphael, South - Michael, West - Gabriel, North - Uriel.
Approach the bowl of water so that when you chant/talk the power of your voice moves it a bit and creates small waves. Water has the magnificent ability to absorb to energy of chanting. Our energy vibes changes the magical potency of Water. So focus and chant! Here is a prayer you can chant.
In the names of Gabriel, Uriel, Raphael and Michael,
and in the names of the Angels of Protection and Exorcism,
Holy powers of the Water, Holy powers of the Light,
Cleanse this water and enhance it with Love and Might!
I advice you to say the chant 3 or 7 or 9 or 40 times, depending on which number you feel is more suitable and magical for you. Every time the chant ends, grab the bunch of Basil and stir the water clockwise one time.
When you are have finished chanting the Holy Water is ready. Drink a bit. Then soak the Basil and sprinkle the Holy Water all over yourself (first) and then your house. You can chant cleansing verses of your Book of Shadows or any Sacred text your prefer. Store the rest for future use. The ritual is over.