Lifehacker summarized an excellent article by Jason Bean suggesting we write email in the reverse order our software masters want.
1. Place your attachments;
2. Write the body;
3. Write the subject;
4. Fill in the recipient.
I've always written the subject of my e-mails last. I'm trying to build a habit of making the subject line relevant and avoiding subject lines that say, "re: re: re: re: ..." I'm getting there but I think trying out Jason's method for awhile may help. It certainly makes more logical sense.