Now that I've gotten us through the fact that not everyone agrees on memory types, I will admit that I'm not always sure when a mnemonic is memory and when memory is a mnemonic. I'm not a strong advocate for memorizing music that's already in one's fingers, and, as a general rule, I never listen to recordings in order to get to know the music that I'm working on.
That all said, let's presume that, in the early stages of memorization, just about everything is a mnemonic. The big advantage to this is that you won't develop tactile memory early on. This advantage will play out later when you might experience self-doubt during a performance; you'll have your mnemonics to rely upon.
Landmarks are mnemonics on a grand scale. I make them a part of my daily routine, and I find that they are essential to a successful memorized performance. But landmarks don't come right away. What about memorizing a few measures a day?
Repetition plays an extremely significant role in the memorization of even the simplest passage. You might find yourself repeating the same measures over and over again. The goal should not be to create a tactile memory experience, however. It can be used to create aural memory, but that's a hard thing to maintain when a piece is being learned from scratch.
My repetitious practice creates a comprehension of pattern. I like the Wikipedia definition of pattern: "a discernible regularity in the world or in a manmade design." In musical terms, that pattern could be a simple regularity of notes, and it could also be the regularity of harmony or rhythm. It can be any combination of those three, and possibly even more elements.
Presuming that you've already created a phrase-influenced landmark in a piece, repetition of that phrase should help you discern the patterns therein. But be careful: don't let your repetition ingrain tactile memory. This is where a timer and metronome become important. Limit your time with repetitious practice while also keeping your metronome slow so as to avoid tactile memory.