The word "Spirit" is heavily overused in our culture, mostly because we lack a cultural understanding that the denizens of the spirit world are not unified in form or function. Rather, they are different and have their own tribes, social structures, matriarchs and patriarchs. Some follow rigid rules and restrictions, while others are lawless and have no such limitations or boundaries.
As a result, dealing with their interference appropriately can take a variety of forms, beginning with the most simple of rituals and ending with brazen, forceful rites of expulsion. Which you choose to use depends most heavily upon what you are comfortable with, but also upon the nature of the entity you are attempting to remove from your space. There are times where this banishing can be achieved with a light tap, and there are times where the use of a sledgehammer will be necessary....sometimes literally.
So we'll start small and work our way up to more forceful means of responding. Of the methodologies used, the burning of sage is the least offensive. To do so effectively, procure for yourself a bundle of sage that's been ethically harvested and sanctify it appropriately. If you're Christian, the Lord's Prayer & Hail Mary will do. If not, and you'd like something a bit more sorcerous in nature, use this prayer:
"Spirit of sage, waken and hasten to me
Enchant this lovely bundle, help to set this space free.
Loosen the hold of demons and troubles dire,
As I set alight your base matter through the use of fire.
Genius Loci of various skill
Abide my laws, do my will.
Those present and of ill intent,
Leave now, swiftly - be no longer present."
Repeat this prayer as you make the rounds through your space, ensuring that the smoke touches all that might require purification. I would recommend opening windows and letting the light into your space, as locales untouched by light have a tendency to draw near things that flee from it.
If this has worked, you'll experience a sense of peace, after which you can fill your abode with warmth and good cheer. Be mindful of this need to refill the space with pleasant energies, as ANY time you clear out a space, you've emptied liquid from a jar - it must be filled to the brim once more to ensure that nothing else takes up residence in the space you've cleared.
If cleansing with sage hasn't been effective for you, and you need a slightly more nuclear option, procure for yourself Artemisia vulgaris (Mugwort), being mindful not to confuse it with Artemisia absinthium (Wormwood), for the herbs have different affinities unto themselves.
As before, you will make the rounds, but this time your attitude should be less peaceful in countenance. Instead of asking others to depart, this time you're demanding, gently yet firmly, that the entities who have taken up residence take their leave of you.
Use this oration:
"Spirits of place with ill intention,
This before me is due prevention
Of all ill and harm one'd seek to create,
And with it I send you elsewhere to seek your fate.
Leave now, gently and without trouble or harm,
For I seek to reclaim this space, making it safe and warm.
Leave now, for you are unwelcome here.
This space is reserved for those I hold dear."
Mugwort is suggested, in this instance, as its temperament is more aggressive than that of sage. Spirits are generally rather offended by it, and it can be a useful means of warding off their influence. That is the reason for it being chosen for this purpose.
To speak on offensive herbs, from a folk magic perspective, the most potent among them is rather easily recognized: Asafoetida, or Ferula assa-foetida. Its considered to be an "aromatic", and its commonly known as Devil's Dung. It smells awful to us and worse to spirits.
If sage is a gentle "please leave", mugwort's a "You need to leave, now." Asafoetida is in a class of its own, and it could be seen, accurately, as an herb that says "Get thee the f*** out of my house!" There are accounts of it being placed on coals to ward off the dead, demons, and other intrusive entities, and I can personally attest to its efficacy.
Just be mindful of using it around the house, as it stinks to hell and upsets everything around you...often to a visible extreme. This is what you use if you want to tell everything within a mile radius to go away, so bear that in mind.
You can couple this with a prayer, but its not needed. Such is the nature of this herb.
In addition to the rootwork means of sending spirits packing, there are plenty of invocations that can be used to this extent as well. For instance, procuring for yourself a Medal of St. Michael and saying over it these words can provide a strong charm against Evil:
"St Michael the Archangel, defend us in battle.
Spare us the wickedness of the Devil and his Horde.
Act as a shield between the Righteous and the Fallen,
Vouchsafing us before the Lord and granting us his fury."
Play with this and get creative, as there are a great number of ways through which one might safely remove encroaching entities without an insane amount of work.