As it turns out, we could keep going with all kinds of tips for making successful email campaigns, so the final ones I am writing about now and the last of the "prevalent" ones that we see regularly.
Consider Preview Panes - Many of your email recipients may be viewing your email in a preview pane with graphics turned off. You need to consider this happening and frame your emails appropriately. You may want to start your email with some text first and then add the graphics later down the email. If you email is one big graphic, you may be shooting yourself in the foot.
Emails should be as short as possible - An email needs to have targeted information that hopefully can be scanned quickly by the recipient with the most important issues up top. Don't build up your email like a written a book. You need to write the email so that the first thing they see will be the biggest and the best part of the email with the later info just being details.
Consider mobile devices - Many mobile devices only have a view space of 320 wide. So many people are using mobile devices that you may want to consider forming your email so it will look good in both normal computers and mobile devices. This can be a lot to consider, but depending on the audience you are targeting it is something to consider.
Now obviously every time you send out an email campaign it is hard to consider all the tips and strategies you have and still make the email look good in all circumstances. There is definitely a balance, and there are some things that are more important than others. I find that small tweaks to email marketing strategy can change effectiveness many percentage points. Email Marketing is not a "static" event. Just like any marketing effort, create and then evaluate.