I hope you're not talking about your Bug......Anyways, if coil springs are sagging this is a quick fix instead of replacing them.
http://www.jcwhitney.com/autoparts/Product/tf-Browse/s-10101/Pr-p_Product.CATENTRY_ID:2005889/p-2005889/N-111+10201+600003419/c-10101

Its our 4door gold  camry, maybe you have seem 1 or a  million of them . My 4 teens are a getting heavy,  and I think and the poor little cars arse be
dragging,  i'm gona try one of 2 of them spacers .  it should to the trick

Do i just jack up the car and these spacers slide in or is it tricky work

From what I remember, you jack the car up slip some spring clamps in the coils and tighten them enough to slip the spacers under or on top of the coil. We never slid them between or we would have to take the spring out wind the spacer in then put the spring back in. There are also these large nuts I remember using where they go in between the coils and you put a ratchet and give them a twist to open the coil. Thes sometimes tended to fling out on some bumps though. Then they would shoot out from the car and bust the car next to you.

YEah, what he said.  I'd look at just replacing them.  You could try used, but you may want to check for new as well.  Some aftermarket parts stores can get factory type coil springs now through companies like TRW and others.