how do you preserve geraniums from year to year

Do you mean Pelargoniums? Most people I know take cuttings and some take them indoors if you don't have a heated greenhouse.
Actual Geraniums are hardy.
Sorry I don't know more.

if you do mean bedding geraniums (lollipop flower heads in reds, peaches, pinks, whites - pelargoniums really) then you can overwinter them. Dig them up, cut the top growth down by two thirds, till you've got something with about 2 inches of stem left, pull off the leaves. Find a large pot or box or container, fill with mix of sand and spent compost, or sand and multi purpose compost. "Plant" the plants in that, puff them with Green Sulphur Dust (garden centre, powder) and keep somewhere dry and frost free. Get them out again in late February, pot up in proper compost and start them growing indoors, put out again in May.
Or, if you don't live in a cold area, do what I do (I live in London); cut them down just the same, shove them all in a big pot with compost and leave against a warm, sheltered and preferably sunny wall, OUT OF THE RAIN and hope for the best - it's the damp that kills them more than the cold.
If they're hardy Geraniums (cranesbill type) then you don't need to do anything.

That's interesting Bamboo....I've had nothing but failure trying to overwinter Pelargoniums! So you say cut the plants hard back to a couple of inches and keep them bone dry? Do they need light?

When I used to do this, I used to stick them in a plastic lined cardboard box, a shallow one, put the geraniums in and then leave them on the top of a wardrobe, near a window, for the winter, in a generally unheated room. So they did get a bit of light, but not much. And you pull off any leaves on the 2 inches you've got left cos if they drop on the soil later, they go mouldy...

SO, just so I'm clear, you're left with little green sticks sticking up with no leaves at all? Do you need to make sure there are nodes or buds or something? It does sound rather drastic!

Well, okay, take the stems down to 3 or 4 inches, if you're more comfy with that, but do remove the leaves - or you can wait for them to fall naturally, but that means you'll have to check the pots/box all the time in case some have fallen on the soil.

I forgot to say, the object of this exercise is to keep the plants dormant, but alive - you don't want them growing during the winter, they need a rest.

I just bring mine in and stick them on the windowsills....they'll flower all winter with a bit of light, heat and water :)

Yea, they do, Crazydi, but then you end up with leggy, woody plants when what you want is fresh, new growth in the early summer.

I've got about 40 plants Crazydi - not enough windowsill to go around! lol

So far so good with my ger/pers. I shorten them. Take off any suspect leaves. Put those that will fit in a mini greenhouse against south west facing wall. Fleece up the really big pots all together, with the fuschias in big pots, in a huddle. Include pots in the wrap. Peg up with fancy clip pegs in pretty colours to stop wind unravelling fleece. Spring.... replant in new top layer of soil. Provado drench if evil weevils around. They romp away. Some bloom over the winter too. Have to keep an eye on them. If not rust can reign supreme. geraniums can be tougher than you think.

That's interesting Dorjac - what part of the UK are in you? I did have a couple geraniums survive outdoors a couple of years ago (unprotected), but I think that was a one-off.

I am in Essex on outer edge of London . Last winter had some cold spells and they got by OK. They do survive in the ground but never bloom well. Like everything else relish a bit of fussing over, IF you have the time and want some specials to keep going. I'm useless at cuttings. No room for a greenhouse

I lived in Essex for a while and I think it's generally a couple of degress warmer than here in the west mids. Got a ghouse, but too cold in there in winter for geraniums, but I could do as you say and wrap them up in fleese INSIDE the ghouse I suppose? Tried them in porch last year - complete disaster!

I think they would survive Sid. Especially if clustered together. If you want a standard to survive, pipefoam or a soil sack round the stem and include in the cluster. Have you seen 4 seasons garden? They use fleece freely. It must work for them as they seem to be horticultural magicians

Think I'll try it - thanks Dorjac :-)