When you create your scrying mirror you can add items to it to help with divination.
Stones; Amethyst, Citrine, Hematite, Lapis, Obsidian, Quartz, Tigers Eye
Symbols can be used as well depending on what you are drawn to. Such as the Pentagram, Eye of Ra/Horus, or the rune Lagu.
You can also burn certain herbs to aid you in divination such as;
Angelica, Bay, Cinnamon, Eyebright, Mugwort, Mullein, Myrrh, Sandalwood, Willow, Yarrow
The color candle you use is up to you. White is an all purpose color. Depending on what you are scrying for you may want to use a different color such as blue for healing.