Monitor Won't Stay Raised Up

Everytime I raise my  monitor (it's an LCD, not sure what model number) to a higher level (slide the screen up), it just falls back downto about half way then friction will just stop it. It doesn't even lock in place or anything. How can I get it to lock in place? There's a button on the back of the stand and one on the back of the monitor for I'm guessing raising/lowering the monitor but they don't seem to work or I'm not doing it right. Is there some sequence or something for locking the monitor so it stays up?