I've had to use that approach on the harder ones occasionally. I've found the solve sometimes requires seeing that X is either Y or Z, then "what if" X=Y and follow the conclusion (on a notepad) listing the consequences for awhile (A=B, C=D)...
...and if that doesn't lead to a contradiction, then look at X=Z and hope that there's a clue that does conflict. If A can't be B then X can't be Y so it's Z.
After awhile it feels less like logic than guessing. I don't know if this the right way or not.
