Great Question!
Software Development is a broad area so the first thing you should do is select specific niches you want to market to.

The Simplest Way: Think of existing projects you've worked on.. What were the customer's needs? What did they ask you? What did you respond? Make a list.

You'll likely find that the same needs and concerns pop up over and over again with clients and prospects. Now pick one specific need and do the following:

1. Create a headline that matches the need
2. List the main benefits or features
3. Set a "Call to Action" (make a call, submit their e-mail, etc)
4. Address all the possible concerns they might have in their head and answer them using a conversational writing style.(Think of how telemarketers always have the answer for your next question).
5. Always keep your call to action visible

(Repeat for every niche you pick)

You can do this in a landing page (online), brochure, or even direct mail - the same principle applies. The most important thing to keep in mind is targeting: only target people who will likely be interested in that specific product/service. You can run as many campaigns as you need, just keep each one as specific as possible.

Remember, a focused effort is way more effective than a broad one.

Give me a call if you have any additional questions!