What are the beliefs and practices of Evangelicals regarding ecumenism?

I want to know what Evangelical Christians (ECs) believe regarding ecumenism and how they practice it. A very practical example is when a person converts interdenominationally. How do ECs make the convert feel like his/her conversion to EC does not imply that his/her entire faith journey up to that point was invalid since they used to believe different to what they now do? Another practical example is where an EC wishes to not make Christians from other denominations feel like they are belittling their faith because they, as an EC, hold to their views while fellowshipping with them.