From the moment someone sets foot on your website to the moment they pay, you must be monitoring the attrition rates at each step. Inevitably some of your marketing efforts will always be wasted when people quit throughout the process, but your goal should be to minimize dropoffs.
Start by attacking the weakest step in the funnel - where are the most people being lost? Is it an issue of explanation? Credibility? Clarity on the call to action?
Keep what your users are saying in mind as you look at this funnel. Is user feedback correlating with dropoffs in any step? For example, are a lot of user complaining about the introductory tutorial not working for them or being unclear? Are support calls usually about the same topics?
This funnel data, together with user feedback to make the data concrete, will become your priorities and very clearly state what you should be working on the most. Focus on those bottlenecks to increase the conversion of your visitors to paying customers.
The following images are the Ecquire funnel for example. We use Mixpanel to track our events which makes this super easy to build once you're collecting the data. The attached funnel shows our conversion at each step, from the moment a user arrives on our website to the moment they pay us, and everything in between.
Funnel 1-5
Funnel 4-8
Funnel 7-11
Funnel 9-13