So you want to increase your open rates. Here's a video quick tip in which MarketVolt President Tom Ruwitch explains how to make that happen.
If you want to increase the open rate for the next email you send, make the email you last sent more relevant, more interesting, more informative. Open rates go down when people don't like what you're sending them.
Don't worry so much about subject lines, don't worry about some of the other factors, just make your emails interesting, informative, helpful, and interesting. Not too pitchy, the more interesting and informative your content, the more likely that people will continue to open them, week after week, month after month, regardless of your subject lines and all those other factors. Interesting content, that's the key.