iOS 12 has a quick way to share your password (though you should, of course, do this with care). When someone is using the same Wi-Fi network your phone is on, you'll get a notification.
By tapping "send password," they can get on the network without having to manually enter complicated passwords. To make this work, both users need devices running iOS 11 or 12 with both Wi-Fi and Bluetooth turned on.
(This how-to is based on my experiences and info on Apple's support pages — where the images sometimes come from.)