Intro: How to Make Your Own Homemade Arduino Uno R3
Here I am using 5V mobile charger instead of LM7805 (This version uses a 5V regulated power supply). It's simple and save some space on board. You can you LM7805 but after that you have to use a higher voltage supply that's why I'm using 5V constant charger.
Step 1: How to Make Your Own Homemade Arduino Uno
Before moving on, check out this image. It's a great resource for learning what each of the pins on your Atmega chip do in relation to the Arduino's functions. This will clarify a lot of confusion behind why you hook up certain pins the way you do. For even more detailed information, take a peek at the datasheet for the Atmega168 (short version) (long version). Here's the sheet for the Atmega328 (short version) (long version)