From time to time I stumble upon one of roules in this manifesto. I strongly recommend to get to know them and just try use use them.
Right now for me the first one is the hardest :( Fight for Pareto - dropping features. This is many times connected with Synthesis and working in company/team when there is someone else that designes and plans what to do next in product.
Points in manifesto aren't new, and they can be found in many other manifesto's but I think that it's worth a couple of minutes to read them again from time to time.