There are various questions that could be asked during an interview that could indicate an offer is forthcoming, for example, the hiring manager may ask, “what is the earliest date that you’d be able to start?” they also may ask for your availability to come in for a second stage interview. Asking about your availability for next steps and informing you that there is another stage in their interview process is a positive sign as it indicates that they are already planning to invite you back. Additionally, if the hiring manager talks about potential packages, compensation and how it would structurally work could indicate that they are thinking ahead to you potentially being part of the team.
The length of an interview is not necessarily an indicator of a job offer as although it can be a good sign that the hiring manager has not dismissed you immediately (for example after just 10 minutes) it could be a sign that they are still questioning your abilities and are therefore digging deeper and opening up their line of questioning.
The most important element of an interview is often the rapport built between a candidate and a hiring manager. Sometimes the conversation can become less about work and more about getting to know you. This is often a positive indicator as it means the interviewer has already bought into your talents and they are now trying to ascertain whether or not you will fit in with the team/company on a cultural level. A candidate can be the best person for the job on paper but fitting in with the company culture can be equally as important as ability.
You may be asked if you have time to meet with any other members of the team straight after your interview, this could be so the hiring manager can see how you engage and interact with other team members and is a great sign. Furthermore, if you’re invited back for a less a less formal interview to meet other team members or a chat in a less formal setting, it is an extremely positive sign that a job offer may be forthcoming.
Listen to your gut, you will often get a feeling if you connect or not with the hiring manager, and often this will be the deciding factor.