What is the most important process before, during and after a sale?

before the sale, you (or your team eventually) needs to start planning the whole operation (market intelligence, value proposition, market strategy, goals and ambitions...). 

Once this first step is done, you need to identify potential customer leads (inbound & outbound lead creation, social media mkt, business networks activation...). 

Then, you will have to qualify the generated leads, through establishing communication chanels with prospects in order to identify their needs and may be discuss details of upcoming sale opportunity (prezentation date, product demonstration...). 

Once all of this is done, you can run the sale, often through an on-site meeting to get the customer acceptance, before discussing pricing, quantities, payment terms...This step is generally referred to as The Closing. 

And finally, comes the after sales support, where you must establish a permanent line to treat and follow up clients issues, and run Customer satisfaction surveys to be sure your clients are happy with what you provide them (Products & service quality).

Hope i answered your question, 

ILIAS