Summoning is not something I have tapped into deeply; however, I do have some prior knowledge of it after seeing it around so many times on the internet.
If you do not know how to make something or someone leave then I wouldn't advise you to let that something or someone enter. Summoning is not something to be taken lightly , in my opinion. It requires a good amount of knowledge and planning. Randomly summoning something is also found disrespectful to some people. I'm surprised people know what "demon" they want to summon anyway. Spirits shouldn't be, according to popular beliefs, summoned without any logical or meaningful reasoning. It is strongly important that you also protect yourself as well. This can be done by creating and being in a circle, a spell, a shield, you name it.
To answer your question, if you know anything about spirits then you'll know that demons are just the same as any other spirit (maybe except for deities) according to different practitioners. I, personally, have found it easy to simply ask a spirit politely to go away if they are in my bedroom or even in the bathroom while I am in it. It works for me but there are various other methods. You may have to search for some online or come up with your own form of banishing something (that is if banishing would be the correct term). If you are a beginner to this then I would definitely go with some more traditional methods such as the Lesser Banishing Ritual of a Pentagram, different chants too, saying verses from a written scripture such as the bible, or even simply praying to your deity or some sacred person/symbol of what you believe in. There are plenty of methods out there so look deep.