get into the operational characteristics:-How to bias them,gain equations,hfe,etc
and (4) do it on real circuit, look at it in the oscilloscope, make mistakes and had scratching, and alot of it. if you still cannot figure out why, (5) ask in the forum. if you dont get answer dont lose hope, do (4) and (5) indefinitely (infinite loop) until you find another better thing to do.
The logical thing is probably to go back & find a new version of (1),(2),or (3),which may better answer your question.
The problem is,that if something goes wrong with a project,many people assume they have an error in construction,so they tear it apart & rebuild it over & over.
If there is a mistake in the design phase of the project,OR a faulty component,they get the same result each time.
The trick is knowing which problem you have.
It makes more sense to fault-find the first iteration,rather than going round in circles.