Here are some strategies that I have used in learning new repertoire. I have had the most success in combining numbers 1, 5, and 6. All I have continued to use at some point, and I encourage you to also try combining at least two different methods in conjunction with number 1.
Use the Met- This goes without saying, but always use the metronome. If it has subdivisions, turn them on. You want to make sure that the rhythms you are playing are correct and exact, not being lazy with them or the tempo that they are in.
Bar by Bar #1- Practice each bar separately until you are comfortable with them. Once each is familiar, put them together by slowly adding a new bar.
Bar by Bar #2- Go through the entire piece by repeating each bar a number of times (I recommend 20 times). This can be with or without a space of some sort to account for difficult or impossible situations caused by the repetition.
Technical Practice- Find every technique presented in the piece and practice them separately.
Problem Spots- Locate the most difficult passages and analyze the technical, physical or situational reasons for the difficulty. You may find that the passage, if separated into smaller pieces, is easy to play. As you begin to put them back together, getting comfortable with the transitions between the separated parts of the passage is key to its complete execution (similar to #1).
Recite the Piece- Sing aloud the entire piece. If this must be done at a slower tempo to utter the rhythms, do so. Be sure to include all dynamics, grace notes, accents, everything, and make it as audible as possible.
Read the Piece- Similar to #6, read through the piece, like a book, but as if you were actually performing it. Make sure you are reading in tempo and with precise rhythmic integrity. This separates the physical engagement and puts the focus all on the mental aspect and knowledge of how the piece goes.
Plan the Stickings- Go through the piece and write out stickings that you feel will work in your favor musically. I say musically because, phrasing choices made in #5's method will influence the way you choose to play the passages. You are completely free and allowed to simply write out a sticking that works purely on a physical level, but don't forget to take into account how those stickings will make the piece sound musically, not just on an execution level.
Add Reminders or Instructions- As you go through the piece, you may find that certain passages turn out better when you are in a certain mindset or physical awareness. When and where these instances occur, write a note to yourself about what you must do or think about to execute the passage properly. This can be written either before or right on the passage.
Play and Sing- Go through the entire piece by playing and singing at the same time. This forces more engagement and conviction with the phrasing and audible contrasts of the piece.