I have someone's name, address and number. However, I have never met or spoke with him, and he has no idea who I am. I know he has a need for a specific kind of software, which I can provide.
How do I approach him? Should I call him? What should I say? Should I directly go to his office? What should I show?
Ideally you want to find someone who can introduce you (for example use LinkedIn) - this will make life much easier.
Once introduced, explain that you have some knowledge in [whatever it is you do] and ask them about their problems in that field. Don't push that you have a product. Ask questions. Listen to the answers. Understand the magnitude of their problems, and estimate their pain (preferably in terms of cost).
Once you have this information, you're in the best position to start talking about solving te problem and selling your product (assuming it is suitable and cost effective).
If it was me, I'd write a letter/e-mail of introduction, rather than cold call or suddenly turn up as that can come across as confrontational, and could give the wrong impression.
In your letter I'd mention what you do, and how you could be of service to them. You could refer to some previous work you've done for other customers, and provide him with contact details, so it's kind of like a CV in that respect. Really sell your skills and such so that he'll have no option other than wanting to talk to you, but do not lie, that'll destroy your reputation in a heart beat.
I would NOT mention pricing at this stage! Instant turn off!
Also explain how you came to know what this person was after too, was it via a mutual friend, a business card, something you checked on their website etc...
You should get some kind of response, if not, then after say a week or possibly even two weeks, I'd either fire off another letter/e-mail (or possibly both in case of spam filtering etc).
I'm not sure if any of this helps, but in your situation, that's what I'd do.
Another way of reaching Corporate decision makers is through events or other common ground, meet them in person and then follow up with a contact email, if he/she is really busy you may need to make an appointment with his/her secretary. In the first approach is essential to listen his needs and talk about solutions to problems. In second interview is critical to point out how your product meets his needs, and of course you would need to point out costs/investments.
You have to get in front of this person.
The best way is through an introductory meeting. See if whoever provided you the contact details can set a lunch meeting up.
If that isn't possible then you need to call this person. Don't email, those are very easily ignored. I know, because I ignore them all the time. ;)
The purpose of the phone call is to take them to lunch. When you get them on the phone be sure to drop the name of the person that gave you his/her info.
Assuming you get a lunch, ask questions and generally listen. People like to talk about themselves and what they are working on. Somewhere along the way you'll be able to interject about how your product solves their problem. If interested, they'll ask for more info. Be prepared to give an immediate demo, but don't push for it. Instead see if you can present in front of their team.