What is a resident?

A resident is someone who has contracted a room for payment. This is a needed person in your hotel. The normal important time for this is when the License law applies. 'Non residents can not be served alcoholic beverages outside licensing hours' [local laws apply]. The majority of cases start when someone has had to much or to little alcohol and wants more. You can refuse to serve alcohol to anyone who is, or appears to be under the legal age or intoxicated. You (the bar staff or licence holder) has a duty not to allow unruly, offensive or drunken behaviour.
Another good habit to get into is the policy that bar staff are not permitted to serve alcohol in the bar without checking a copy of the registration card, NOT the door key. This does not apply to restaurants where alcohol is served with the food under a 'supper' licence.

What is a guest:

A guest is someone who is not resident, but uses your facilities. Such as the swimming pool, or bar before closing time, or the restaurant. The terms guest and resident are interchangeable, but here we use them to make a distinction. This is someone you want in your hotel.

What is a Non resident

This is someone who does not fit into the above categories. There can be several people here; a person who has come in to ask questions, a friend of the above, a 'floater' or ad hoc in the restaurant. This is someone you would like in your hotel.

Who is undesirable.

Person who does not fit into the above categories, but wants to abuse them. The person may have started out as one of the above but through their actions you now longer want. Simple case for this is where someone decides to have a party in their room, wakes up the neighbours and then decides to rearrange the bedroom in the style of the the latest art show. A person who attempts to obtain services without paying, a person who is abusive or threatening.
These should all be dealt with diplomatically, at first, ask them if they are a resident. If unsure, ask them their name and why they are doing it or what they want. Then start with the 'calm down' and finally head for the 'stop or I will have to ask you to leave'. Once you have go to the leaving stage, you need to remember two things.