Everything in this post is probably covered in even the most basic 'how to blog' guide, but most eve bloggers aren't especially ~professional~. Hopefully someone will find this useful.
In this post I will be linking examples of what I'm talking about. This is done to provide illustration, not as a callout, so don't get butthurt.
Nobody likes ads. If you aren't making actual money, get rid of them.
Most of your readers will be subscribed using a newsreader. When the newsreader imports your posts, it will usually change the default text color to black and display the text on a white background. However, if you manually change the text color, the newsreader will use the manual color.
This means that if you change text in a post to a color which is hard to read against a white background, your readers will have a hard time reading it.
Put another way: Never, ever, ever use yellow text. More generally, any color which isn't easily visible against both light and dark backgrounds should be avoided. If you must change text color, mid-range blues and greens are usually okay.
You can have your blog display popular posts and blog stats and pages and followers and a search box and links to every eve blog in existence and every eve site in existence and labels and a profile and the tweet fleet stream and seven different ways to subscribe, but that doesn't mean you should. What you're actually doing is drowning your content under a river of crap.
If you don't personally use a gadget, get rid of it.
Labels should be useful tools for your readers to find different types of posts. This means:
Labels should be meaningful, not something you make up on the spot. Define them for yourself in advance.
Labels should be applied consistently. Clicking on a label should display every post relevant to that label.
Labels should be widely applicable. If you have 100 labels and 90 of them are only used for one or two posts, you're doing it wrong.
If you have a huge banner causing your content to start halfway down the screen, you're doing it wrong.
If you have multiple banners, you're doing it wrong.
If you have a text title, then a banner above or below the title, you're doing it wrong. They should be co-located.
Backgrounds should not be brighter than the content of the blog. It's visually distracting.
Unless you really know what you're doing, don't try to use a static background image. If you think you know what you're doing, test it on multiple monitor sizes anyway, and even then make sure the image fades to the page background color.
If you have a background image or colored background, be extremely careful using transparent backgrounds for your posts. If you must do this, the transparency should be very slight (e.g. 5-10%) and you should be very careful that it does not interfere with reading.