Of course, any 'tip' that is universally useful, you would have thought the advanced student would work it out for him or herself. Plus their own way of doing things. And for the things they don't work out, that's what a teacher is for. So I was never really convinced about the effectiveness of tips. However, in as far as they can go, and with the thought of planting the seed in a brain, here's my 'tip':
Don't think of key signatures as, now I need to remember such and such sharps or flats. Instead, think in the key you are in. Play the scale with one finger (non legato). Transpose a well-known song (Twinkle Twinkle little star) into that key. Get used to always knowing what key you are in - there will be just a few times it might not be clear - that is fine, just make sure you know why it's ambiguous.
Oh and one more tip:
Once you know the piece, but still need to practice is, practice it from the end. Practice the last bar. Then from two bars to the end. Then from 3 bars to the end. And so on. That way, you know the end the best, and you always feel like you're going into better known material. Never allow yourself to stumble from the beginning into the first mistake, and then from the beginning into a different first mistake.