I use Prop. to abbreviate property or properties according to this website. Now I am wondering if there are common rules in English writing for abbreviating words.
You should not abbreviate words on your own because you don't know exactly how reader can get to your point.
On gcflearnfree.org, you can have an idea how it is created. The basic rule is :
Abbreviations are usually formed using the most recognizable letters from the word or expression. This makes them easier to remember, and easy for others to read. It's almost like the letters are clues that point to the original word or expression.
But, in most cases, you should use abreviations which aleady exist by using dictionary lists like Oxford English Dictionary.