Prepare in advance.
Have an outline (rather than a script) with the general thrust plus any specific questions, however, be willing to go with the flow.
Coach, prepare, rehearse your guest.
It is almost never a good idea idea to simply wing it even with folks who have done it a zillion times. A prior discussion of the topic, emphasis/interest points, and with noobie interviewees, one or two dry runs will make the actual recording seem more natural, less disjointed, with the person feeling more comfortable.
Note: given the type of podcast described, simply sitting and chatting will require significant editing: always keep your target audience(s) in mind, it is their time you will be requesting.
Must have as good sound quality as possible: superb is best
At least minimise background noise such that it never distracts.
A brief introduction without selling.
Note: with the type described it may not be in play, still worth remembering.
Never more than a minute. 10-30 seconds is a good range depending on podcast length.
Better: a transcript.
People have varying degrees of available time. This is why it is often worth taking a (for example) 60 minute podcast, however delightful, and splitting it into 2-30 minute segments, 4-15, etc. as options. Requires splicing in new intros but that is minor.
Given that likely audience(s) are not all going to be old and hard of sight you may want to record as full video and then extract the audio for an additional stand-alone podcast.