There are several platforms designed for blogging. The one that is used the most appears to be WordPress.
There are two forms of WordPress available. They are the wordpress.com site and the WordPress download that you host yourself.
With the wordpress.com site you can get a free site but you will be tied to a xxxxxx.worpress.com domain name. This may be fine for you when you are starting out, but if you are going to be using the internet to make money I would suggest using a domain name of your choosing to match whatever your site is about.
There are paid wordpress.com sites where you can choose your domain name if that is what you want to do.
I personally have my own hosting and can choose the domain names I like, (providing they are available).
I can have an unlimited number of domains hosted with the hosting package I have. I also have a separate hosting account as part of my affiliate connection with WA. This one only allows WordPress accounts but it does give me 25 accounts.
The WordPress blog download is very simple with most hosting packages. It is usually just a couple of mouse clicks needed to download the package. One downloaded the set up procedure is fairly simple to follow.
Whichever route you choose to take your blogging will follow the same or very similar format.
When it comes to posting on your blog I would say to post at least once weekly. If you have something that will be of interest to your readers then by all means post more regularly.
If you wish to post about vastly different things, then I would suggest more than one blog. For example, if you wish to blog about dieting and then decide to branch out into fashion, I would keep the two blogs completely separate from each other. You can of course set up links between them but those interested in dieting are not necessarily going to be interested in fashion and vice versa.