In a December 2008 Datran Media survey of 3,000 marketing executives from Fortune 1000 companies, 80.4% of respondents identified email as the strongest-performing advertising channel for their brands, and 82.4% said it helps increase sales through other channels.

For companies interested in generating similar results, the first step is to improve open rates through the use of effective subject lines.

We asked DJ Waldow, director of best practices & deliverability at Bronto Software; Ben Chestnut, cofounder of MailChimp; Dylan T. Boyd, VP of sales & strategy at eROI; and Greg Cangialosi, CEO of Blue Sky Factory, to weigh in on what makes a good subject line.

Here's some of what they came back with:

1. Keep it concise, 35 characters or less, according to Cangialosi. "Longer subject lines will be truncated by some email clients," he said.
2. Make it about the reader. Boyd suggests writing to the audience, not at them; keeping the customer lifecycle in mind; and personalizing the message based on profile or behavioral data. "Always pushing your sales agenda will reduce the open rate and conversion rate," he said.
3. Make it actionable by providing a sense of urgency and a clear call to action (think verbs!). "Put the most important information and the key call to action first," recommended Cangialosi.
4. Ensure your message is simple, clear, and informative. "If it is not simple, [is not] understood, and doesn't give a clear action or value, then it will be passed over," said Boyd.
5. Avoid ALL CAPS and exclamation marks. "[ALL CAPS] feel like you are shouting for attention and not being respectful of your subscribers' time," said Boyd. Chestnut added: "If there are 100s of other emails in the inbox with subject lines screaming for their attention, sometimes whispering is the best way to stand out."
6. Include your brand. "This is especially important if your company name (from line) is not that well recognized," said Waldow.
7. Draw attention with buzz words like "Twitter" or "YouTube," said Waldow, who also offered, "I like to think about subject lines as headlines in newspapers. Does it catch enough of your attention to read on?"

For an idea of what works for us at MarketingProfs, here's a look at the Top 100 most effective subject lines from the MarketingProfs Get to the Point! Newsletters.

See whether any of these catch your attention...

1. Potty All Night Long
2. Four Blogs You Should Be Reading
3. Seal Your Pitch with a Kiss
4. Release Me Please!
5. A Week at IKEA
6. Twitter for Timeliness
7. I See Riches on the Horizon
8. Newsletter No-No's
9. A Doctor Who Only Makes House Calls
10. Widget for Dollars
11. Did He Really Call It a 'Nymphomercial'?
12. I Am McLovin!
13. Playing Tag
14. The Freeconomics of Online Media
15. How Customers Are Like Lab Rats
16. Sidle Up to the LiveBar
17. The SEO Rapper
18. Burger King Tells a Whopper
19. Get 'em to Gawk
20. A Coffee Klatch for Every Marketer
21. Laugh 'Til You Cry
22. Shameless Marketing Stunt
23. A Super Bowl Strategy That Paid Off
24. How Saying the Least May Achieve the Most
25. Loaf Run
26. Senior Makes Site Accessible
27. Oh, Count the Ways You Can Annoy a Journalist
28. Ranting and Raving
29. Jingles 101 with Dinah Shore
30. When Your Video Isn't Viral
31. On-the-Fly Creativity
32. Put That Checkbook Away
33. Branding Tips from the Queen of Burlesque
34. Time to Yelp!
35. Get Over It, Kid
36. Do You Have Peripheral Vision?
37. Rules Schmules
38. Create a Customer Walk-a-Thon
39. Is Your Newsletter a Must-Read?
40. Keeping Up With the Kremplers
41. Subject Lines: Tell, Don't Sell
42. Cool Open-Rate Stats
43. Podcasting is Easier Than You Think
44. Don't Be a Twit
45. My Blog, Myself
46. Think Small to Win Big
47. Social Security Shenanigans
48. Would Your Blog Get an A?
49. A Resolution You Can Keep
50. How to Measure That Long Tail
51. You've Been Punk'd ... and Wiki'd
52. The Cold, Creamy, Refreshing Story of Social Media
53. The Wisdom of the In Crowd
54. The Angel in Red Speaks to Us
55. Glad You Could Make It!
56. Springtime for Twitter
57. Using Tricks of the Journalistic Trade
58. We're Still Married to the Past
59. I Like 'em Small and Focused
60. Get Gored
61. Will Dance for Gum
62. It's Alive! It's Alive!
63. conferences">No More Boring Conferences
64. A Clearly Good Marketing Plan
65. Yammer to Keep It Together
66. Passengers: Your Captain Has Screwed Up
67. Invite. Engage. Inoculate.
68. The Slow Art of Customer Seduction
69. How to Blow It in Five Words or Less
70. Give 'em a Good Tease
71. Taking the Email Plunge
72. Analyze This
73. The Deviant Approach to Creativity
74. A Gentle Step into Web 2.0
75. Sprechen-Vous Italiano?
76. We're Short on Euphemism Today
77. The Revolution Will Be Widgetized
78. Inspiration from the Swat Team
79. Why You Want Customers to Notice Your Zits
80. Help Your Customer Live the Fantasy
81. Remember Me?
82. Pepsi's Scheme Fails Taste Test
83. Mind Your E-Manners
84. Time to Step Up Your Blogging
85. Go Where the Current Leads
86. Look at Me. Now CLICK.
87. Warm Up Your Thinking Cap
88. What You Can Learn From Starbucks' Mistakes
89. Dumb It Up, People
90. Those Jerks Are Talking About You. So Talk Back!
91. How to Be a Better Blogger
92. A Permission Marketing Primer: Picking and Choosing
93. It's Time to Socialize, People!
94. Stick to the Script!
95. Loose Lips Sink Ships
96. Customer Service the Lexus Way
97. It's Talkification Time!
98. Plurk It, Baby!
99. The Cocktail Party Rule
100. On Target