While the following article is almost 20 years old and pertains to MTG, I point it out as it's an excellent bit of gaming strategy that is relevant in almost all games. Ironically, I think the article will end up being more relevant to Nu5R, due to the design of the game allowing for more flexibility. If you can get past the MTG specific examples and get down to the meat of the post, I think you'll find it to be a helpful reminder when playing competitively.
http://www.starcitygames.com/magic/fundamentals/3692_Whos_The_Beatdown.html
Basically it boils down to a player recognizing when they need to alter their strategy and take a different line of play, maybe even one they are not comfortable/good with, in order to increase their chances of winning. Nu5R's mechanics appear to allow players to adapt to each other on the fly, much more so than any other game I can remember. This is something I'm extremely excited about as should introduce us to a level of strategy many of us may have not experienced.
I've often heard the phrase "don't play the cards, play the man/woman." I don't think Old5R truely gave us many opportunities to do both. I think that saying will prove to be less cliche in Nu5R, so it should be important to familarize yourself with various types of play. The more comfortable/proficient you can become with them they better prepared you will be to adapt to your opponent.
Edited by Ishi Tonu