[Tijdreiziger]

There is a shortcut to remember this: 'e.g.' for 'example given' (and therefore, 'i.e.' for 'that is').

('E.g.' doesn't really mean 'example given' in English - it means 'exempli gratia' in Latin. But it's a useful mnemonic.)

[xenophonf]

I also use "in essence" for "i.e." even though it's actually 'id est' in Latin.

[JohnFen]

In my mind, when I see i.e., i think "in other words", and when I see e.g., I think "for example"