Do read the "Terms of Service" before you create your new personal e-mail ID.
Think a little about the name you want to choose. The obvious: firstname.lastname@ ... ... ... may not be available since no 2 e-mail addresses may be the same.
Choose a name that will be a easy for other people to remember and that somwhow describes you, your interests or what you do.
Choose a password that is difficult to "hack" and that you can remember. Your password should be about 7 characters long; use Capitals, small letters and special characters to make it safer. Example: my first dog was named Bella, 1DogBella* might be a password I can remember.
Don'ts
Don't choose names that might be embarrassing late in your life; eg. sexygirl@abcdef.com, or alwaysdrunk@ uvwxyz.com
Avoid names that end in numbers even if they are suggested by the mail provider. Do you really want to be susan107@asdfgh.com?
Don't choose passwords like: 123456 or qwerty or abcdef.