Geraniums

BML

I have a dozen or so Geraniums in large pots which are beginning to go over in that the flowering stems are losing the colour petals.  I'm taking them off by bending them down until they snap of but I'm left with some very healthy leaf and I have no idea what to do and I would like to keep the plants for next year.

Could someone please offer me an idiots guide as to what I should be doing.

Many thanks.

Dovefromabove

Are these really geraniums (Hardy) or Pelargoniums (frost tender) which are sometimes sold as bedding plants and erroneously called geraniums (very confusing). 
If they’re hardy geraniums there’s nothing you need to do. 
If they're  pelargoniums they need to be moved to frostfree conditions (conservatory/kitchen windowsill etc) for the winter. 
This may help https://www.gardenersworld.com/plants/the-different-types-of-pelargonium/

Ceres

If they are pelargoniums you can cut them back hard and put the plants in a greenhouse or conservatory and hope that the weather doesn't get too cold. Providing we don't get a long cold snap they should be okay. They do not need to be watered much during the winter, in fact it is a good idea to neglect them and leave them fairly dry. 

The stems you cut off the plants can be rooted in water, vermiculite, or compost and will provide more plants for next year. The cuttings will need to be kept indoors where it is warm.

Big Blue Sky

Do all of them need to be cut back @Ceres ?
 I have saved a few trailing pelargoniums that only developed a decent length at the end of the summer. I was hoping I could overwinter them as is so they have a head start next spring...

Obelixx

Keep them frost free and well lit and don't over water.  An indoor windowsill will be fine as long as it's not above a radiator.  Still worthwhile to take cuttings tho, just in case.

Ceres

Big Blue Sky said:

Do all of them need to be cut back @Ceres ?
 I have saved a few trailing pelargoniums that only developed a decent length at the end of the summer. I was hoping I could overwinter them as is so they have a head start next spring...

I always cut back all my pelargoniums when they are moved under cover. Pelargoniums are never too keen on being moved to a new location and I think that keeping them small over winter causes them less stress. They certainly don't suffer for being clipped and quickly put on new growth in spring. It also stops them growing too leggy.

Big Blue Sky

Thank you @Obelixx and @Ceres. I shall trim them lightly and try to keep them happy over winter. I found plug plants were quite expensive to buy this year so hopefully I can keep them until the next season.