Excellent article, Here are come more points :
1. Not everything has to be OOP, often it is too much overhead, each method and object call consumes a lot of memory.
2. Do not implement every data structure as a class, arrays are useful, too
3. Don't split methods too much, think, which code you will really re-use
4. You can always split the code of a method later, when needed
5. Make use of the countless predefined functions
6. If you have very time consuming functions in your code, consider writing them as C extensions