First, check the pads.
Then, if you have a sax light, check to see if you have any leaks. You can do this simple procedure yourself.
Check above the F key, there should be two adjustment screws on a long rod... see them?
This adjustment is easy to do.
Run the light into the top of your horn and settle it where the F and G# are.
Now, hold down and open, repeat with either your lower Bb or ...