If it's email, my experience has been keep the touches valuable and consumable. By that I mean, don't send them a 2 page email with all kinds of content about how awesome your company is and why they should use your product. Take the education marketing approach. Send them little nuggets of useful information or data. If you are selling an analytics platform, give them some insightful analytics they can immediately benefit from e.g. "did you know that 50% of people who walk on a car dealership lot end up buying a car in the next 30 days... be sure to capture contact information from EVERYONE that steps foot on your lot".
The recipient of that email drip feels they got a real valuable data point that is also actionable and they'll remember it came from you. When they're ready to buy, you'll be top of mind.
Links to articles are also great for drip campaigns e.g. "hey, we saw this interesting article on customer patterns for car dealerships and thought you might find it valuable" -- of course, if you guys did the analytics and produced the white paper that's good too.
Key is to mix it up. Frequency is ok, if it's useful.
Your touch points will depend on your target customer.
A good starting point would be to analyze your different audiences and developing a buyer profile for each. One of the components of each profile would be the channels they use to gather information (the digital places they hang out).
From there, you will need to develop a content plan for each channel, then create and publishing relevant content that meets the information needs of each audience.
Possible touch points would be email (permission based), social media, direct mail, online/offline ads, etc.
Take away the specific industry and you still need to look at basics.
Map your steps out by the level of commitment they require. A whitepaper requires less time and commitment than a webinar, for example.
You should have a series of responses mapped out for every action in the funnel AND every inaction.
From there the key is the present the CTAs in the right way. This really does need to be specific to the path the person has come down. By the time they've invested a significant amount of time going through your funnel your communications should seem like they're written specifically for that person.
