I have Suse 10.2 on 2 laptops each with 1Gb RAM and desktop with 1.25Gb RAM. All 3 now have swap partitions at about 1Gb and seem to be happy. I have read here and on other forums, that once you get to 1Gb of swap, unless you are doing very large math calculations, or working with huge graphic files, then more swap doesn't help much. On the desktop I do webdesign, and regularly have Quanta+, gFTP, GIMP, Gwenview and a 2 or 3 browsers (Firefox, Opera & Konqueror) all open at the same time, and get almost no swap activity except when opening a new graphic file.
How big do you need to make the / partition? Well again that will depend on what you are doing. If you have a lot of big applications open at once, then the /tmp & /var directories can get big (temp files and logs). From my experience, if you have only 3 partitions (/, /home & swap) the 1Gb for swap, 15Gb for / & the rest for /home should do. I am now starting to use a separate /home/data partition, so that if I do an install that needs to blow away my /home partition I don't have to back up my data. You could also have separate partitions for /opt & /usr/local, where applications will put there files, and for /log where log files go. That way if anything there gets very big it won't cause too much hassle. On a server, you would probably have a big /var/log partition, and separate partitions for /web and /mail.
Partitioning is to personal taste, how much work you want to put in keeping it tidy, and how often you need to update/re-install the OS.
Here is a good guide to partitions
from the tutorial section of this forum.