It sounds like you are having trouble with general nonogram solving techniques. Every puzzle in the game has been thoroughly tested (I would know!) to confirm that there is only ever one solution, and that the player never has to make guesses about where to mark. There are no secret solutions, there are always logical moves you can make to correctly solve a puzzle!
Here are some tips:
Don't guess! Look at the information available and mark tiles that you know must be filled or empty. Each bit of information builds up and gives you more clues as to your next move, until the puzzle is complete. If at any time you think you have to guess, you have missed something important. Guessing will introduce bad information into your solution and can make solving much harder.
Don't just mark squares you know must be filled, mark squares that you know cannot be filled with an X mark! Knowing where tiles cannot be filled is every bit as important as knowing where tiles can be filled. There are many puzzles where this information is the key to making progress.
Some more reading that might help: