I sometimes get emails that are obviously spam when I read the subject line. Rather than look at them, I delete them by Control-clicking the email and selecting Delete from the contextual menu. I can then go to my Trash folder in Mail and repeat the process.

Another tip: Beware that some emails can have hidden links. I have accidentally clicked in a blank area of an email and been directed to an unwanted web page.

Look for symbols substituted for letters, obvious misspellings, and spurious email addresses from the sender. I received an email, purportedly from someone I knew, that had wsorchesttra as the return email. Her correct address is wsorchestra (one t). The sender pretended to be this woman, asking me a favor if I could send money to a needy friend of hers. Naturally, I phoned her and she had been on the phone with AOL for two hours trying to resolve the problem (all her contacts had been hacked).

Be vigilant! There are lots of dirt bags out there with no conscience or morality.

Just a reminder that you do not need to click on every e-mail in Mail to then control-click Delete. You can select multiple e-mails (shift-click for a continuous group of e-mails; command-click for discontinuous groups of e-mails). Then control-click in the highlighted group, or use the Trash icon in the Mail Toolbar. And like you said, they are obviously spam when you read the subject line, so you don't need to click on them and read them.