You want to make sure that your email marketing campaigns are as effective as possible, right? The best way to do that is by testing. Testing your email marketing campaigns is important because it's the easiest way to optimize the success of your marketing campaigns and help you get the most from your list.

Most of the below tests can easily be run with split A/B testing - which means that one segment of your list receives one version of the email, and another segment receives another version of the email. Make sure that you only change one element of the email at a time, otherwise you won't know which difference in the two emails is changing the way your readers react to them. You should also make sure that one of the emails - the control email - is the way that you would normally write the email, without changing anything.

Without further ado, here's the top three tests you should be running in your email marketing campaigns:

1. Call to action testing. The call to action (the part where to ask your readers to...well...take action) is one of the most important parts of the email and has the most to do with your conversion rate. A weak call to action will result in less people clicking through to read your post or look at your ad or buy something. It's a good idea to always split-test your call to action every time you send an email to your list, just to make sure that you're continually improving it.

2. Test mailing days and times. Sending your email at a different time can make the difference between it being opened and read, and it languishing at the bottom of a pile of unread emails, only to get deleted without ever being read. There's no hard and fast rules for the best time to send email - it's all going to depend on your audience and their habits. So test several different times and see which result in the highest open and click through rates.

3. Test subject lines. Your subject line is as important as your call to action, if not more so, because it has to compel readers to open the email and read it. The best subject lines pique curiosity or immediately tell the reader how they'll benefit from opening the email. Subject lines are another element that should be tested as often as possible to make sure that you're continually improving them and that you're getting the highest open rates possible. After all, if people don't open the email, they can't click your links, read your copy, or buy what you're selling.

Other things that might be worth testing include the pricing of your items (for example, $29.95 vs. $27 vs. $30), the tone of the copy in the email (hard sell vs. soft sell), or the formatting of the email (lots of graphics vs. very little graphics vs. no graphics). You can also test a certain email with specific segments of your list and see how it converts, compared to the list at large.

Testing your email marketing campaigns takes a small amount of effort to set up, but it'll pay off tenfold. Take some time today to set up your first split test, and start seeing results.