You are on a job search. You will most likely eventually be asked for references. The time to prepare for that is now, before your interviews start. Not in a knee jerk response for a request.
At minimum a potential employer will want to confirm you had the job you say you had. They’ll ask about your dates of employment and title. They might also ask what you were like as an employee. Were you punctual? Did you take initiative? What was your attitude like?
If you provide a reference that will only give the basics, then don’t expect any fireworks on the part of your prospective employer. You want your references to be able to speak highly and positively about skills and experiences, but you also want them to hold credibility. The singing praises of your cubical mate aren’t going to get you far. The same words from a supervisor are good. If your previous boss is willing to vouch for you that’s even better. If you are a recent grad a professor can attest to your abilities and drive. In general, you want to have two or three professional references you can count on as references.
When thinking about people we could call on as references, it’s important to consider how much weight their words will carry. If your reference is an expert in something related to what you are applying for that’s amazing. Someone who has seen you do (and excel at) a variety of different things will be able to speak confidently about your abilities.
Prepare them well in advance
The time to let someone know you are including them as a reference is early on in your job search. Give them time to think about you and what you can bring to the table. When you know they might be called on, give them a call. Let them know the kind of job you are applying for and the sorts of things you would like them to focus on. Confirm when it would be convenient for someone to contact them so they have time to give the reference their full attention.
Now that you’ve prepared your references, go out and get yourself in a position to need them!