Take time and care to write the most compelling teaser or subject line possible. It's the best way to ensure that the rest of your copy has a chance to present your case to your prospective supporter.
Commandment No. 11: Thou shalt not try to be who you aren't
This commandment is broken when nonprofits seize an opportunity to raise money when they don't have the systems in place to respond properly to the need. Think about any natural disaster in recent years; inevitably, a few nonprofits jumped on the "Us, too!" bandwagon and raised money without having programs in place to efficiently use the money to do the most good.
Pamela Barden is an independent fundraising consultant focused on direct response. You can read more of her fundraising columns here.