1 - Understand the main processes that sales orgs use (MEDDIC or its variations) - you don't need to follow it in all its details but yes in the general idea

2 - Understand what is the problem you're solving and how companies can benefit from it

3 - Understand how companies actually do procurement

4 - Outbound sales are the ones that sucks the most. A rejection is just a rejection, don't take it personally (one part of having actual sales people is being a more impersonal process - they care about the sales but a rejection is taken less personally)