Texas Hold 'Em Poker Strategy is a very extensive topic and one that could be discussed for years on end without any definitive answers being unearthed. That is why not only thousands of books have been written on the topic, but also why new books continue to be written that offer enough originality to be successful when they sell on the shelves. While different poker strategies will focus on different things, they are all variations on two basic themes; figuring out what you have and figuring out what your opponents might have.
When you play Texas Hold 'Em poker, figuring out the hand that you have is one of the utmost important things that you can do. The way to figure out the hand that you have and where it might fit in the hierarchy of hands is to take a look at your two down cards (the only cards that are unique to you in the hand) and consider them against the community cards that are in the centre of the table. The main thing to consider is of course your two cards before the flop hits and this is because you want the flop to hit your cards so hard that you have one of the best hands possible at each stage of the game. If you start with marginal two cards and the flop hits, there will likely still be a lot of hands out there that can beat you. If you start with strong two cards then that is a lot less likely.
Another thing to consider is how much the strength of your hand comes from your starting two cards and how much the strength of your hand comes from the community cards. The more strength that comes from your two starting cards, the better it ultimately is for you. If, however, you have a hand that relies on four cards from the board and it is not a nut hand (like four clubs on the board and you having the ace of clubs), then you need to be very careful about how you proceed because of the ease that someone else could have one card in their hand that has you beat.
Because people are so poor as players at the lower limits of hold 'em poker, you can master the what you have part of poker strategy and conquer lower games quite easily. However, if you want to advance through the ranks and become a great player, you need to start developing a proficiency in what they have as well. This proficiency can only be exercised by practice and there is nothing in books that can help you with it aside from an understanding of things like physical tells and betting patterns. Understanding the different types of players and the betting patters and tells that they tend to give off is a good first step, but only through playing with a player and seeing them on a regular basis can you truly hope to get a handle on exactly what makes them tick.