semicolons?

so i pretty much never use semicolons in my writing. Actually i probably have at one point or another, but typically, not. So i thought it a good idea to find out how to use the things, then i can start using them.
So there is pretty much about 5 rules to using semicolons in writing. They read as follows:
1. Use semicolon in place of a period, when seperating two sentences without using a conjunction.
2. Use before words such as, for example, therefore, and however.
3. Use them to seperate units of a series when the units contain one or more commas.
4. Use the semicolon between two sentences joined by a coordinating conjunction when one or more commas is used in the first sentence.

Okay so i know that sounds really confusing, so it might be beneficiary to look at this websight and see some of the examples that they use.

http://www.grammarbook.com/punctuation/semicolon.asp!