Hello! My name is Humberto Valle. I'm the founder and CEO of Unthink Digital Marketing. We do inbound marketing services for companies and we actually have some clients who have hired to do just that. The short question to you is: You need to build relationships and leverage your expertise. Online that translates to creating good content as an excuse to introduce yourself, company, and solutions and pitch to companies. Or reverse, have them find you on their own by coming across useful information that is not sales but just helpful.

Hi, you can approach the head of IT department by email or phone. I suggest you practice your sales pitch first. You don't have much time (about a minute or two) to convince them that you're different and better than others. You may want to check what your competitors offer and promise before you contact any company.

You need to understand what problems they have before you can propose a solution/service/product to them. Also, there's no way to sell unless you have access to these people. If you don't have the network, you need to start growing it first in order to understand their problems and sell to them.

Options (quick brainstorm, you can do better):
1. Look for the 1000 CTOs and 1000 CIOs of each of these companies and figure out a way to get to know them
2. Start off with smaller companies so you can 'level up' and avoid wasting your bullets on the hard-to-get intros in option 1
3. Go to conferences or read online to better understand what problems they have and why its worth hiring the resources you would provide