First off, you'll want to make sure your tub and bathroom are clean and tidy. Dim lighting, like from a salt lamp or candles, are ideal to set the tone. You'll want to play some kind of meditative music during your spiritual bath. Healing frequencies, classical, instrumental — whatever brings you into a state of peace.
As you draw your bath, you can add your favorite bath salts, herbs, or essential oils. Something relaxing like lavender, rather than an uplifting citrus scent is probably best. Flower petals can also be added to the water. If you have any healing crystals you'd like to line the bath's edge with, now is a great time to do so. Having a glass of ice water and a cup of hot tea within arm's reach of the tub is another key element to this ritual. If opening a window for some fresh air would help relax you, then go right ahead. This can be particularly refreshing in the colder months when the breeze is crisp.