reducing Postscript file size

[Fred C]

Didn't find an EASY (I'm not a nerd) to use answer for that common
question :
How can i reduce the monstrous size of .eps  pictures to be inserted in
my thesis written with LyX 1,0,4 on Linux 2,2,13?
A simple color picture of Linus in jpeg makes 17 kb, saved as grayscaled
.eps it results in an horrible (to save on a floppy) 1,6 Mb!!!
Help

Fred (Montpellier, F)