All of my diary-writing tips are below the flip...
My Quick Diary-Planning Tactic
After I research but before I write anything, I come up with a one sentence version of "What is this diary about." In this case it's simple: This diary is about my ideas on how to write diaries.
Next, come up with a few sub-topics. They might be bullet points to support your main point, or if you are telling a story chronologically, they might just break up different periods in time (i.e. The 2000 Election, The 2002 Election, etc).
Make Sure Someone Can Tell What The Diary Is About
That probably sounds obvious, but I can't tell you how many times I've had a migraine and gone through the following experience: I click on a diary that has a title like "You won't believe what Bush said!" I don't necessarily want to read the whole thing - I just want to know what Bush said and I can't find it anywhere.
If I read the whole diary, I'd know what outrageous thing Bush said. Except, my head hurts. I look at the sentence before the flip, the sentence after the flip, I skim a bit... I get frustrated and scroll down looking for a blockquote somewhere. I read the last sentence of the diary. Nada.
Since I don't like when people do that to me, I try not to do that to other people. I want to make sure that if they click on my diary, they can find what they are looking for fairly quickly.
I try to write some sort of creative introduction to my diaries (usually, not always), but I also try to put a sentence as close to the flip as possible - right before, or right after - saying "In this diary, I will talk about..." (maybe not in those words, but it's important to get that point across)
That gives the reader enough information to decide whether or not they want to read my diary. Without getting that info up front, someone who is trying to decide whether or not to read your diary might just decide to skip it.
Break Up Your Diary With Headers
There is something intimidating about a computer screen full of tiny words. Headers help break that up.
I use the sub-topics I brainstormed up front as my headers typically.
Truth be told, I'm not a very structured or organized person. Often I don't put in the headers until the end. I just think up a topic, come up with a theme, and write until it's finished. But THEN I go back and try to add headers to it, to make it easy on the reader.
If someone wants to give my diaries a 30-second skim instead of reading them, they can figure out what the diary is about by just reading the headers and nothing else (or at least, that's my goal). Then if you want to drill down and actually read the text of the diary - you'll know what you're getting.
Use Short Paragraphs
Seriously. Short, short paragraphs. Like, a few lines. If you write a diary and you find you have a long paragraph, look for a natural place in the paragraph to split it in half.
dKos has tiny text and very little white space. It's hard to read if people don't break it up into bite-size chunks.
Give Action Steps (This is for Elise)
I always feel bad about telling people something without telling them what they can do about it.
For example - this week I wrote about mercury in fish. The point of the diary was that Bush is a hypocrite because he preaches a culture of life and yet his policies endanger hundreds of thousands of babies born each year from mercury in fish. I included links to websites that have lists of safe fish to eat.
Have a Beginning, Middle, and End
The beginning and middle kind of take care of themselves - then don't let the diary just fizzle out.
In the beginning, you told your readers you were going to tell them something, whether it was the crazy thing that Bush said, or why Democrats will definitely take back the House and the Senate, or whatever. In the middle, you hopefully covered that topic.
When you finished writing about that topic, come up with a brief conclusion. You don't need several paragraphs. Even a sentence will do. You want to make sure the reader leaves your diary with the point you were trying to get across - this is your chance.
The Fun Part...
Assuming someone is actually reading your diary, not reading just the title, the headers, and the pretty pictures you posted - you've got an opportunity.
You can be funny, be informative, be persuasive, be whatever you want. As long as your diary flows somewhat, cites its sources (and choose credible sources to begin with), and doesn't pledge allegience to the Republican party, you are doing great.
Everyone here starts out as a nobody, except for senators and other politicians, but with time - and with consistently good diaries, you will build a fan base. People who share your interests and your sense of humor will seek out your diaries. It's not a bad way to meet new friends :)
Those are my strategies - what are yours?