Running a B2B demand generation campaign is a bit like playing on a pinball table.
You can put money into the system and get more balls into play by launching the spring. You control the paddles around the pinball table and you have to make sure you press each one at the right time, just when a ball is about land.
Each ball in play represents a potential customer of yours. The paddles are the various marketing or demand generation activities you have at your disposal. One paddle might represent sending out a newsletter; another might be interacting with potential customers through Twitter; another still might be presenting at an event.
Your goal is to push the balls progressively to the top of the table where they might 'convert' into sales-ready opportunities. You should also aim to prevent the balls from falling through the gap at the bottom. If they do fall through, they are lost opportunities and you'll have to replace them by putting more money into the system.
As a startup you won't have a lot of marketing material, case studies, videos, or blog content. You'll only have a couple of paddles on your table – perhaps a direct email or a cold call. You certainly can push a ball all the way to the top and generate a sales-ready lead using one paddle in isolation, but it's difficult. You're relying on a bit of luck with your timing; and the chances are that a lot of balls will end up falling through the bottom.
As you add more and more paddles (marketing activities) to your table you are effectively giving yourself more chances to keep your potential customers engaged with your organisation. You reduce the chance that good prospects are lost, since you have more ways to interact with them.
You still need to have management oversight of the whole system once it's up and running to ensure that the paddles are being activated at the right time and in the right order. You also need to know when the system is working well enough that you can invest more money with confidence that you'll get the right return. Learn to play this game effectively and you'll have a predictable flow of sales opportunities.