I think the main thing to remember is that your blog and Helium have different audiences. Most blogs are really just personal journals that happen to be public to the world. You're probably writing a blog for yourself or your friends, maybe your family.
On Helium, your audience is instantly global.
This means that the slang and shortcuts your friends are familiar with may be incomprehensible to your readers here. Keep your audience in mind and it will no doubt have changes in your language usage and tone. That's a good thing.
Breaking it down, here's a few things to keep in mind:
* Use good grammar, spelling, and punctuation, as well as proper word choice. 'Belie' may not mean what you think it means. Some of your readers won't be native English speakers, so help them out by being clear.
* Don't use too much slang. Sometimes slang will be relevant to what you're writing about, and some slang is more ubiquitous than others, so I'm not saying use no slang at all. However, if it's something you'd say to your friends, but not your parents or your boss, then you might want to consider rephrasing.
* Don't be too personal. People only care if your cat puked if you're writing about cat food. You don't need to tell people your medical problems, your age, your gender, or your location on this planet, unless it's relevant to what you're writing about. Would you tell a complete stranger you've just met for the first time in a coffee shop that you suffer from hemorrhoids? Even medical professionals don't want to hear about it outside of the office.
* Stay on topic. You can ramble to your heart's content on your own blog. If you have more to say on a related topic, then find that related topic and write some more there. If the topic doesn't exist, then create it.
Finally, think about what you're writing. Internet chat moves swiftly and you have time to clarify your point in your next comments. Blogs can be easily edited or deleted if you change your mind. Helium posts can't be, except by that weird Leap Frog concept. So be sure to get it right the first time.
Happy writing!