Word searches typically have words hidden vertically, horizontally, and diagonally. Harder puzzles can also have words in reverse order, making even short words very difficult to find. One of the simplest tools you can use to complete a word puzzle is a ruler _ block out the horizontal lines one by one and read across until you recognize a collection of letters that form one of the phrases you're searching for. Next, move the ruler vertically line by line. Finally, do the same for diagonal lines. This simple first pass at the puzzle should allow you to discover a large number of words.
Once you've found a lot of the letters in the puzzle the best tactic is to look for areas of the grid where there is a lot of blank space. If you don't see any of the missing words, the remaining words in that space are probably reversed or diagonal. Scan for any phrases that match in this area and you're likely to find your remaining words.