Firstly, Google Drive has been part of Android for some time now. That means you don't have to download any additional SDK since all you need is the Google Play Services library that comes bundled with every Eclipse/ADT installation.
1) Set up the Google Play Services project as a library in your Eclipse workspace (for a breakdown of the steps involved, see this guide), and add it to the Google Drive Quickstart Android application (download it here)
2) Create a new project in the Google Developers Console.
3) We are interested in giving our app access to our users' folders and files on Google Drive, so we need to enable OAuth.
Once your project from Step 2 has been created, go to Credentials and click "Create new client ID."
Copy the SHA1 key and paste it into the Google Developers Console.
You should see the Client ID on the page after you submit the required information.
To read more on what you just did, click here.
5) Make sure you go into Google Developers Console and turn on access to the Drive API under your project (select your project, click on "APIs and auth" in the left naviation pane, and then select "APIs"). Note that there are two things: Drive API and Drive SDK. Earlier, I kept getting an error that looked like this: