If you get much spam, you probably have a good idea of what some "spammy"
subject lines are. I can tell you that the messages I get that often almost
get deleted without reading are those without subject lines or with subject
lines all in lower case or caps or with misspelled words. Although I often
use humorous subject lines on some of my emails to friends, for business
purposes your best bet is a subject line that describes the subject as
specifically and accurately as possible, perhaps with a personal reference
if it's going to someone you know.
Also, make sure your mail client is set up to display your first and last
name (or initials and last name or however you would ordinarily sign a
message), not just your email address. This is especially important if your
email address is anything other than your name (or something like it) @your
ISP or company Web site. Would *you* open a suspicious-looking message from
elephant144, say, or maddog2020?