In order to win and play solid poker you need to understand the basic fundementals of poker. One basic poker strategy is "calculating outs".
Calculating your outs is determined by figuring out how many cards left in the deck can make your hand.
For example if you are holding an Ace and King of diamonds and the flop is Ten(diamonds), Jack(diamonds), Four(clubs).
You would have (4) queens (for a straight), (3) Aces (for top pair), (3) Kings (for top pair) and (8) diamonds (for a flush). The total outs you would have is (18)