This should go without saying, but you would be surprised.
Never leave home without your business cards. Make sure your cards include your name, address, important phone numbers and an email address. They should also include a business logo and slogan or tagline. You should give out your business cards generously, even two at a time. The more cards you have circulating at any given time the more helpful they can be.
Don't forget to download a business card app. Yes, you can create a digital business card too! The benefit of this version of a business card is that you can quickly gather the person's name and either text or email them your business card.
Remember: those who follow up, WIN!