Have a professional email address, voicemail, and business cards.
Avoid emails like email@example.com or firstname.lastname@example.org. You are going to want a Gmail account- they are the most professional looking email addresses.
You are also going to need your first name and last name as your email. It should read email@example.com. If your name is taken, try something like firstname.lastname@example.org.
Use Google Voice to protect your personal phone number and get a professional number that forwards to your phone.
You need to set up a professional voicemail that says your first and last name, thank the caller for calling, and mention that you will get back to them.
Get thick card stock for your business cards, it makes you look more successful. Getting the cheap, flimsy, super glossy cards look amateur and everyone will know you invested the minimal amount in representing yourself.
This shows people you take your work seriously.