Is there a mnemonic for when to use уйти vs. выйти?

Question

How do you remember when to use the right verb - or is it simply by memory - or are they interchangeable?

I suppose the same could be said for прийти/войти

Answer 1

Уйти = leave, go away.

Выйти (из) = exit (from some confound -- a room, a building, etc).

Прийти and войти аre the opposites of уйти and выйти, respectively.

Since the question is about mnemonics, the prefix is the key here:

Prefix у- indicates movement from "here" (from the point of view of the narrator or subject) out, elsewhere: ушел, убежал, уехал, уполз

Prefix вы- indicates movement from within to outside of something: вышел, выехал, выбежал, выполз

To illustrate, consider this narrative involving a certain education professional:

Мэри Поппинс:

• Прилетела неизвестно откуда
• Влетела в окно детской комнаты
• Вылетела (из дома на улицу) через парадную дверь
• Улетела в неизвестном направлении

Answer 2

One could use уйти in the meaning of 'leave with no immediate intent of coming back' and выйти otherwise (it is especially the case with выйти).

Example:

- Где Павел? Where is Pavel?
- Он вышел. He is away [but is likely to return].

- Он ушел. He is away [and he had shown no intention of coming back soon].

Edit: examples.