Place <lj-cut text="whatever you want it to say"> in front of what you want to be behind the cut.
Place </lj-cut> when you want to end it, or leave it blank. The only reason you'd really use the </lj-cut> is if you wanted a particular portion to be back on the front page, or if you only wanted to hide a certain portion of the text.
Ex.
I want to hide the thing talking about my favorite color.
This is what I want to hide, this will be behind the lj-cut, about how I love love love the color burgandy.
And this, I want back on the front page.
Would be coded as
I want to hide the thing talking about my favorite color.
<lj-cut text="link can say whatever you want">This is what I want to hide, this will be behind the lj-cut, about how I love love love the color burgandy.</lj-cut>
And this, I want back on the front page.
On the front page it would show
I want to hide the thing talking about my favorite color.
extra: If you would like for something to come up when you hover over the picture you can type
<img src="http://www.url.com/imagename.jpg" title="what you want to say">
Ex. (hover over the image and see a text box pop up saying "johnny depp is awfully pretty")
would be coded as
<img src="http://i2.photobucket.com/albums/y31/kho_mood/icons/johnny%20depp/1.png" title="johnny depp sure is awfully pretty">
(on suggestion from smtfhw) If you would like to change the size of the image, that is simple enough. Keep in mind though, it might screw up the pixelation. In other words, make it look funky.
I'll blow up that picture to twice it's size, which would be 200 pixels x 200 pixels
I wrote a story that can be found <a href="http://www.livejournal.com/users/khohen1">here</a>
or
Click on the picture to go to my journal:
would be coded as
Click on the picture to go to my journal: <A HREF="http://www.livejournal.com/users/khohen1"><img src="http://i2.photobucket.com/albums/y31/kho_mood/icons/johnny%20depp/1.png" title="click here"></a>
There are lots of colors, and my favorite cheat sheet for all the color codes can be found here. You can denote the color either by code # or by name. Either way. I usually go for name, unless it's a particular color I want and don't know the name of.
You can combine all of them into one if you want. IE
<font face="trebuchet ms" color="blue" size="4">
On all font changes
Be sure to put the </font> when you want it to stop. For instance, if you want only one word to be orange, then you need to put the <FONT COLOR="orange"> before what you want orange, and the </font> after to stop it. Otherwise.. you guessed it. Everything after it is orange.
Just hit reply folks. This is brand new, so I'm just answering frequently not known things about LJ to new users. If you have a question, ask it, and I shall answer thusly.
If you'd like the same kind of tutorial I just did, but for HTML specific and not just LJ specific, go here