- they want to have multiple 'demos' with 5 or more attendees which end up being hours long
- you need to work hard to find out whether people you are talking to have any purchasing authority
- they want to have PoC deployed
- they want to have a kind of reviews and special contacts: security, special contracts, special NDAs, etc.
- they never pay invoices
- they are always want to tweak how the product works
In short, enterprise sales are more about relationship and negotiation - so you need to have team dedicated for doing only that (sales, sales engineers, etc.). It is not hard - but just you need to have team and process for doing that. For example, many established companies will have "paid PoC": You want to test our solution? Great. You have to pay first to test it.