There's no easy answer, and some of the "solutions" on the market are a pain. When I send an e-mail and get back a message telling me "I really want to receive your e-mail but I'm not going to unless you answer this e-mail", I ask myself "how much do I really want to communicate with this rude person?"
I use Spamcop, with NO blacklists, just the SpamAssassin filter set to 3. That lets less than 1% of all spam through, and "blocks" about one genuine message a month (based on a fairly careful read through the held mail folder). I Spamcop-report all the stuff to my personal address that it traps. I have a separate Spamcop account for the "official" stuff.
Spamcop isn't perfect, but in my experience nor does it blacklist ISPs unless they have been sending Spam. It's just a pity that it won't blacklist the US ISPs that are the source of much of my spam - rr and verizon - and of course t-ipnet.de, telecomitalia.com, and tpnet.pl. I've blocked the countries .cn, .ru, .hk, .jp, .th, .ar, .mx, .ro and .br so I don't know how much is coming from there these days.