Um... not sure about websites, but the usual tips are:
1. Practice every day, consistently. If not every day, every other day. Set aside time for you without interruptions or obligations to practice.
2. Practice with goals in mind. Have a plan when you sit down at the piano. Do not play aimlessly and hope to improve something while you're playing. Think critically about your pieces. Break them down into issues and order those issues by importance. Look at both the forest and the trees within. You should have a daily goal, a "by lesson" goal (ex: "By the next lesson, I want to be able to do x") and an overall goal for your piece(s).
3. Do not let yourself get overwhelmed or too frustrated with what you're practicing. If it's not working out, take a break. Move to a different piece. Work on a different section, and come back later.
4. I cannot stress this enough. Practice efficiently. Practice smart. The less time you use to accomplish the same thing means more time to do other, more pleasant things. Who am I kidding? Sometimes practice can be fun, but for a lot of us I think it's just something we need to get through so we can do the fun part, ie play the piece at a relatively high competency level in order to enjoy it.
5. Listen to your body. If you're in pain, if something is sore, if it doesn't feel comfortable, you need to stop what you're doing and evaluate how you're performing the action.
Hopefully these are the tips you're looking for, any more specific and you'd need to list pieces, etc.
