Krishna says in BG10.25

"yajnanam japa-yajno’smi"
Of sacrifices I am the chanting of the holy name (japa)

 

A guide to Japa Meditation

Golden Rules for Japa Meditation

1. To obtain the full blessing of Lord Krishna for good meditation, chant the Panch-tattva maha-mantra first:

(Jaya) sri Krishna chaitanya
prabhu nityananda
sri advaita gadadhara
srivasadi gaura - bhakta - vrinda

2. Chant the full maha-mantra on each bead:

Hare Krishna Hare Krishna
Krishna Krishna Hare Hare
Hare Rama Hare Rama
Rama Rama Hare Hare

3. Chant each syllable aloud and clearly. Every time your mind wonders bring it back to the syllables.

4. Listen very carefully & concentrate on the sound of each syllable.

Start of chanting daily and gradually build up to 16 rounds a day.
Try not to leave home without chanting at least 4 rounds and be observant to the peace of your every moment.

Beads and bead bags are available at your nearest temple shop or at the vendors in Mayapur. You can get them blessed before you use them at any ISKCON temple free of charge.
It is advisable to keep your bead in a bead bag.