Debriefing after interview
Immediately after the interview, take some time to sit down in a private, quiet area and write up your interview notes. This will allow you to look over your notes and evaluate the skill set and personality.
If there has been more than one of you hosting the interview ensure that you both sit down together afterwards and go over your notes.
If you do not write concise notes after the interview you may well find it hard to distinguish between one candidate and another. The result will be that you may well offer to the wrong person.
Always be careful of your judgement, you may find it based on the fact you had something in common with the candidate or indeed nothing in common with them at all! Aim to be unbiased.
If you have multiple candidates being interviewed for a position, make sure that each individual candidate's notes are all filed separately so that they do not get mixed up.
Try not to let your emotions come into the interviewing process. It is important that you keep an impartial point of view at all times. They may well have given you the correct answer worded in a different way and you might not have liked the way they worded it.
A comprehensive debrief after every interview will make your job a lot easier. Applying this will make the decision about who you do and do not want to invite back for further interviews and who you would like to offer the position to, a more decisive one.
When assessing a candidate after an interview, look at their personality fit with your department's culture as well as their skill set match, this is equally if not more important.
If a candidate does not match up to all the skill set criteria that you are looking for, but you still feel they would add value to your organisation, consider the possibility of restructuring your department to accommodate them. Consider bringing forward that hire you were thinking of in the near future, as they may easily be cross-trained and you do not want to regret losing them, especially to a competitor!