let the pods dry out / turn brown and then harvest the seed and keep in a paper bag/envelop in a frost free place until next spring. when dry the seed is often pink/black.

If you have the time and you have lots of pods over, why not just save the seeds from the largest pods in the hope that you will have long pods next year?

As above, choosing the ones from longest pods, largest etc. Save the best as seed in hope of improving your stock

Alternatively, save seed from the plants with the most pods, tenderest pods, least pests and/or diseases, etc.

Hi, Thanks for your answers, I only have a postage size back yard, so everything is grown in pots. When should I pot up the saved beans for next years crop,(I don't have either greenhouse or cold frame just windowsills) and is there a better compost other than standard compost that I buy, if yes it should not be too expensive as I'm on a fairly tight budget. Once again thank you for your help, started finding the joys of growing late in life, I'm now in my 70s.
Regards.
Sellina46

I don't start my beans off in outdoor pots until about April/May. I tend to use a John innes type compost as it is more soil based and is less likely to dry out. Hope that helps.

Selina, potting up depends really where you live & last frost dates, obviously Dorchester and Dumfries are weeks apart regarding this date and only you will know the date for your area, it can also vary within area, for instance in a valley or near coast
https://www.gardenfocused.co.uk/adjust-dates-uk.php

I normally start off indoors and plant out mid to late April [south Hampshire] but it's not critical, later sowing soon catches up