Spammers will try just about anything to get their junk past the filters and into your hands. Your job? Don't play their game. Here are some of the more egregious (okay, downright dumb) ploys spammers use to get their e-mail into your in-box.
Gud spelingg. Read a few pieces of spam and you quickly reach the conclusion most spammers are idiots--the messages are rife with misspellings, fractured grammar, and typos. There are two reasons: (1) many misspellings are designed to fool filters, which might stop spam containing the word "viagra" but miss those with "v1agera"; and (2) most spammers are indeed idiots.
Re: your bogus message. A popular tactic is to use "Re:" in the Subject line to fool you into thinking their ad is in reply to a message you sent. Recent examples include "Re: hi," "Re: hey," and "Re: heh." Articulate little buggers, aren't they?
Oops, I just spammed myself. Another trick spammers us is to put your e-mail address in the From line, so it looks like you sent yourself the message. ("You mean I can give myself a low-interest loan? What happens if I don't pay it back?")
Dear Someone_Else. Really stupid dictionary spammers put everyone's name on the To line, then put the first name in the Subject line. Yeah, that'll fool 'em.
Taawwfxqnbeutdyhkefcmw? Sometimes the Subject line is complete nonsense. Sure, it fools the spam filters. But only a babbling idiot (or another spammer) would read it.
Spam that pretends to be spam. I recently got a message with the subject "[Possible Spam] Accuracy: Medium." It was meant to look like a message a spam filter might send you, but it was really a standard come-on for credit repair services. Hey, give 'em credit for being honest.
Spam that sells antispam software. Believe it or not, some makers of antispam software--like MailWiper and Spam Remedy--advertise their wares via spam. Well, that's one way to guarantee a steady market for your product.