If you are a beginner:
i recommend 18-22 Lbs for you, this tension get more elastic. because you are a beginner, you don't have a strong powerful wrist. if you string the racket too high, you will hurt your wrist and arm. i did this stupid thing before.
If you are amateur :
24 Lbs, cross 22 Lbs, that would be good for you, you will feel it that you can easy to hit the high clear to backcourt. Also good for drop shot.
If you already are a good player:
i think when you play badminton over 2 years , your wrist power is improve, you can try 26 Lbs string tension, why ? because when you get a high tension , your racket's face will get stiff, that is very good for net game. good for control. and when you hard smash, you will feeling more power on it. that's why the professional player usually take very high tension (35-37Lbs.)
PS: select a good tension for yourself. high tension can get good control, but request you get a strong arm explosive power.