Different spiritual traditions have different methods for how to cleanse a location. The examples that I will give in this article come from my own background. They are easily adaptable to other spiritual traditions. The basic format of these rituals have much in common with the rituals of other faiths. One element that these rituals have in common is the use of blessed elements (holy water, incense, and candles). They also incorporate basic spell craft (prayers being considered a form of spell craft) whereby the ritual participants impose their will upon the situation or invoke a spiritual being to take action on their behalf.
The most basic form of spiritual cleansing is to focus your will upon cleansing a location of unwanted influences as you physically clean there. In Wicca, there is a tradition of using a besom (ritual broom) to sweep the circle area before establishing sacred space. The circle area is swept in a counter clockwise spiral that starts in the center and moves outward. This is because the counter clockwise direction (known as widdershins by many pagans) is considered to be a direction of banishment. Some incorporate a chant that they use to the rhythm of their sweeping gestures. A quick google search find many chants that you could incorporate into your cleaning.
You can incorporate other elements into your cleansing to make it easier to align your will to the task. Prayers and visualization are helpful for this task. Calling upon one's preferred deity to bless and sanctify a location works to cleanse the location upon a spiritual level. This, however, must be maintained with some effort by the person calling upon the deity. Failure to do so runs the risk of irritating the deity. It would be like you calling upon a friend to clean up a messy room. If you do not put any effort into keeping the room clean afterwards and continually call on them to do it, they will become upset with you for not doing your part.
Walking the boundary of the location to be spiritually cleansed with incense and waft it into the location while envisioning the incense chasing away undesired entities and spiritual energies is a common technique used in the pagan community. It is also done with holy water. The Catholic Christian belief system has several beautiful rituals to consecrate and cleanse locations. These rituals combine the elements of prayer, incense, and holy water. If I recall correctly, there is one that incorporates candles as well.
Which ever method of spiritual cleansing you choose, it is always useful to revisit them on a regular basis when maintaining a location as a permanent sacred space. The act of spiritual maintenance of permanent sacred space helps make ritual work that happens there more effective because the location is prepared for it already. It is also a gesture honoring the spirits of the location and the spiritual beings that were involved in the establishment of sacred space.