Increasing or ensuring the security of your Gmail account is less about technology and more about being careful while using your Gmail account. It is a given that you should use a password that cannot be easily cracked or guessed. Here’s a Gmail blog post on how to choose a smarter password for your Gmail account.
After you’ve chosen a smart password you should make sure that you connect using an HTTPS connection and not the regular connection. When using a computer that is accessed by multiple individuals remember to log out after checking your email. You should also refrain from sending confidential and sensitive information through your Gmail account. Read more on how to increase the security of your Gmail account on official Gmail account.