We target companies with 10-100 employees using a 14-day trial, self sign up model with pricing at $5/user/month.
At that pricing I would include in your advertising that the per month fee is only about the cost of a single cup of coffee. To make that clear, tell them that you'll in fact make their first month free by emailing them a starbucks coffee coupon when they sign up. That initiates your relationship with them as more of a 'social contract', rather than a business one, since you've given them a gift (make sure to include their first name in the starbucks coupon email), and their brain now associates the $5/month fee with just a single cup of coffee, which is money they basically throw away each day anyway. A social contract makes people more committed to your brand, and pay less attention to the cost and more to the relationship. With that said, once you start a social contract, you have to keep it up (keep interacting with them in a more buddy way, in terms of email wordings, things you may send them occasionally, etc), otherwise if you switch back to treating it more like a business contract again they will get pretty offended / pissed. If you want more advice on this let me know.
There is no one best way to land your first 100 clients out the gate. I recommend running small experiments with prospective target markets in order to sculpt the right message and identify the correct market/vertical. An example, I hypothesized that LinkedIn would be the best channel to reach family law attorneys. I proved out that Twitter was a much more successful channel.
If you're specifically targeting your first 100 customers, I would make the free trial much longer. At this very early stage, you're better off with customers using your product than with paying customers. Look for customers 101- and beyond to be paying your bills. So do a 3-month free trial instead - or longer. I would also target customers in the same industry and possibly in the same geographical area. You're more likely to get referrals if you have a universe of users that are similar.
I would encourage to do pre-trial gamified engagement with target companies/employees. Create indirect yet relevant functional experience and rewards those users with something encouraging. It can be a coffee mug, T-shirt or even a month free for product. Then introduce the SaaS software to use.
Pre-trial engagement gamification can be as simple as - Q & A or Take a photo moment or Mention a problem (one your SaaS software can solve) via tweet.
I have given this method a try and seen very valuable results. Indirect relevance in gamification can be extremely helpful.
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I would look for people who are influential in your target market and talk with them individually.
Even though your product is based online, it might be beneficial to start with local chamber of commerce networking so you can meet your prospects in person. If your product can capture their attention, keep them close to you and overcommunicate to get their feedback on what they like and don't like and where they get stuck. Help them build the habit of using your SaaS.
Iterate if you need to overcome roadblocks to successfully adopting the software - maybe make training videos, or add documentation, or make changes to the product itself if there's resistance to using some part of it.
What you want to do is really bond those early users to you and find your evangelists who will talk about your product on social media and livestreaming platforms like Periscope and Blab.
Interview the early users on video using Blab or Google Hangouts or use one of the Skype recorders to ask them how they use the product, how it helps them, how it's made their life easier or their business better, and get their permission in writing to add that to your YouTube channel and then share it on your social media channels, paying careful attention to LinkedIn, since that's where you'll find a lot of B2B customers.
Once you've built up about 5 or 6 of those evangelists, start hosting webinars. Splice the YouTube comments into the webinars so attendees can see how people just like them are using your SaaS.
The main thing is to remember to treat people as individuals and not try to lump them into a group, and really do a good job of babysitting and nurturing those early users of your service.
If you'd like some strategies on finding those people and how to reach out to them, please feel free to schedule a call with me.