Be attentive when you are practicing. Don't just go on autopilot and watch the clock, hoping everything will turn out fine just because you are spending time at the piano. Practice with focus, and have goals. A lot of memory work can be achieved while working on other elements of pieces, as long as one is attentive about what one is doing.
When you come across passages that are difficult to memorize, isolate and focus on them. Do this as opposed playing through entire pieces, or parts of pieces you already know. Don't always practice pieces in chronologically. Break them up, play them backwards, play random measures, play random phrases, etc.
Don't rely solely on muscle memory. You need to use other forms of memory to support muscle memory.
Practice memory recall. Start playing parts of a piece from some random measure.
Practice recovery from memory slips. Intentionally make a slip and work on making a fluid recovery while maintain the performance of a piece. Also practice getting yourself out of wrong note slips.
Something I tell my students: You can't memorize something you don't know.
It sounds ridiculously obvious, but can be overlooked. In order for you to memorize something you need to be attentive to it. There is no use practicing memory recall when you were unaware of that object or event in the first place.